Definitive list of AHC maintenance items (5 Viewers)

[uHu]

VGRS is something I don't have and I don't know how to reset the angle in TechStream, but I suppose you do it under "Utility".
The FSM has an extensive procedure for VGRS under the Diagnostics chapter, with procedures for doing both VGRS calibration and Steering Angle Sensor Initialization, with the t0yota Tester or without.

There is some help here: Steering wheel alignment

 

[saudi]

AHC springs are very light weight compared to normal Landcruiser springs, but I don't know if that contributes more to pinching. My brother's airbags failed because the valve was torn out, probably due to a bad installation, or bad design, and he has a Landcruiser. I don't know which brand he used.

As for price, no idea these days. I looked at them nine years ago.

I haven't heard of anyone putting pressure monitors into the AHC system either. Sure, you can get pressure monitors for airbag systems, and control units to inflate the bags to the desired pressure with an on-board compressor. I guess if you had a laptop with you and the TechStream cable discussed above, you could check the AHC pressure while on the road, whenever you adjusted the airbags.

In line pressure sensors in the AHC system and some sort of monitoring panel would be nice if you were going to use airbags though.

I’ve just fitted king springs from Australia they are slightly up rated for abc and I also fitted Firestone airbags when fully loaded , I run them at 5psi normal 12-15 fully loaded 5 passengers. It glides. Well worth doing I also cranked up Torsten bars using techstream pressures

 

[IndroCruise]

I’ve just fitted king springs from Australia they are slightly up rated for abc and I also fitted Firestone airbags when fully loaded , I run them at 5psi normal 12-15 fully loaded 5 passengers. It glides. Well worth doing I also cranked up Torsten bars using techstream pressures

View attachment 2383825

View attachment 2383826

View attachment 2383827

Hi @saudi,

I have a question ....

I fitted King KTRS-79 springs and at the same time included similar Firestone airbags for AHC from CR5114HP - Air Suspension Helper Kit for Coil Springs - High Pressure .

The KTRS-79 springs have made the ride a little more firm when the vehicle is empty but is very good when heavily loaded for long distance travels. The compromise suits our use and there have been no complaints from Mrs Indrocruise or other passengers!

The airbags have been operated with air pressures as @saudi describes for a little over year in a variety of outback conditions. They certainly are very good for variable loads. Did I really need the King springs AND the airbags? I am not so sure about that. The King KTRS-79 springs were better for my application than OEM replacements and I did not want to fiddle with spacers. Maybe the airbags could have come later if really required. The lighter alternative of OEM replacement springs with spacers plus airbags was considered and may have given slightly more ride comfort as well some ability for variability loads but I am happy with the stronger springs. Anyway, it is done now.

I liked the idea of the additional stone protection that comes with Kevlar sleeves -- but after a year and many height movements from "N" to "HI" and back (as well as movements from time to time "N" to "LO" to "N" and "LO" to "HI" and back when testing AHC pressures and 'globe' condition via HI/LO Test, etc -- the sleeves are slipping.

Raise times have been getting progressively longer -- now about 30 seconds from "LO" to "N" without a load, about double the time suggested in the FSM -- and so I am wondering about friction between the airbags/sleeves and the coils slowing the raise, or, whether I have a tired AHC pump or problematic height accumulator. I am thinking the Kevlar sleeves may come off -- they are not achieving much when the airbag is left exposed.

Anyway, it would be very helpful if you could please advise whether you are experiencing longer suspension raise or drop times since installing your airbags?

 

[saudi]

Hi @saudi,

I have a question ....

I fitted King KTRS-79 springs and at the same time included similar Firestone airbags for AHC from CR5114HP - Air Suspension Helper Kit for Coil Springs - High Pressure .

The KTRS-79 springs have made the ride a little more firm when the vehicle is empty but is very good when heavily loaded for long distance travels. The compromise suits our use and there have been no complaints from Mrs Indrocruise or other passengers!

The airbags have been operated with air pressures as @saudi describes for a little over year in a variety of outback conditions. They certainly are very good for variable loads. Did I really need the King springs AND the airbags? I am not so sure about that. The King KTRS-79 springs were better for my application than OEM replacements and I did not want to fiddle with spacers. Maybe the airbags could have come later if really required. The lighter alternative of OEM replacement springs with spacers plus airbags was considered and may have given slightly more ride comfort as well some ability for variability loads but I am happy with the stronger springs. Anyway, it is done now.

I liked the idea of the additional stone protection that comes with Kevlar sleeves -- but after a year and many height movements from "N" to "HI" and back (as well as movements from time to time "N" to "LO" to "N" and "LO" to "HI" and back when testing AHC pressures and 'globe' condition via HI/LO Test, etc -- the sleeves are slipping.

Raise times have been getting progressively longer -- now about 30 seconds from "LO" to "N" without a load, about double the time suggested in the FSM -- and so I am wondering about friction between the airbags/sleeves and the coils slowing the raise, or, whether I have a tired AHC pump or problematic height accumulator. I am thinking the Kevlar sleeves may come off -- they are not achieving much when the airbag is left exposed.

Anyway, it would be very helpful if you could please advise whether you are experiencing longer suspension raise or drop times since installing your airbags?

View attachment 2385195

I tried spacer first and wasn’t impressed. Yes times are slower and I have a new pump. Also my fluid level is higher !!
But feels great

 

[RPLX470]

VGRS is something I don't have and I don't know how to reset the angle in TechStream, but I suppose you do it under "Utility".
The FSM has an extensive procedure for VGRS under the Diagnostics chapter, with procedures for doing both VGRS calibration and Steering Angle Sensor Initialization, with the t0yota Tester or without.

There is some help here: Steering wheel alignment

Thanks uHu, I’ll read up on that link.
I cleared codes and they didn’t come back. Good.
AHC pressures a still a bit high, but now one of the torsion bars is fully tightened and may need to ‘reindex‘ the bar. I will search for a procedure.

 

[IndroCruise]

Thanks uHu, I’ll read up on that link.
I cleared codes and they didn’t come back. Good.
AHC pressures a still a bit high, but now one of the torsion bars is fully tightened and may need to ‘reindex‘ the bar. I will search for a procedure.

This thread on torsion bars (including re-indexing) might provide some useful background information on torsion bar removal, indexing and re-installation -- the first post includes useful pictures (but not AHC) .....

For those with torsion bar questions

Torsion bars 101 FOR NON AHC VEHICLES First some terms so the search function picks this up: - help with torsion bars - how to adjust torsion bars - reindex torsion bars This all went in Amy's thread but I thought those who weren't subscribes may like to see it. Ok lets try get to the...

forum.ih8mud.com

 

[menancyandsam]

Is the procedure for reindexing the torsion bars the same for AHC rigs.

 

[IndroCruise]

@agaisin at post #3 in this 2011 thread highlights the difference in purposes of torsion bars between non-AHC and AHC vehicles.

It also is worth a look at the Factory Service Manual (FSM) at the following link and drop-down menu on the opening page:

https://lc100e.github.io/manual/

Go to the following tabs in the index panel on the LHS of the opening page”:

“Repair Manual”

Then

“SUSPENSION AND AXLE”

Then

“FRONT TORSION BAR SPRING (Independent Front Suspension)”

The FSM makes no distinction between actual method for removal and replacement (including re-indexing) of AHC versus non-AHC torsion bars but does assume, as @agaisin has highlighted and also as highlighted in multiple subsequent posts by other IH8MUD Members, that the Owner also is reviewing the relevant FSM sections in the drop-down menu headed

“ACTIVE HEIGHT CONTROL SYSTEM (Independent Front Suspension)”

and the sub-section labelled

“ON-VEHICLE INSPECTION”

Again, it is important to be aware of

• the different size and purpose of the torsion bars for AHC vehicles versus non-AHC vehicles (see also this link), and,
• the different hub-to-fender measurements for a stock AHC vehicle in standard condition, specifically, Front 19.75 inches, Rear 20.50 inches (or, Front 500 millimetres, Rear 520 miliimetres) – these approximations are widely and successfully used by IH8MUD members instead of the more finnicky measurements stated in the FSM, and,
• the different work required if a ‘lift’ is being undertaken on a vehicle fitted with AHC (search IH8MUD concerning ‘lifts’ – there are plenty of articles).

Although originally written for non-AHC vehicles and despite the differences from AHC vehicles, the longstanding detailed pictorial explanation by @Gunney also remains useful to all Owners of LC100 with IFS and AHC, and LX470 vehicles.

 

[silver02accord]

@agaisin at post #3 in this 2011 thread highlights the difference in purposes of torsion bars between non-AHC and AHC vehicles.

It also is worth a look at the Factory Service Manual (FSM) at the following link and drop-down menu on the opening page:

https://lc100e.github.io/manual/

Go to the following tabs in the index panel on the LHS of the opening page”:

“Repair Manual”

Then

“SUSPENSION AND AXLE”

Then

“FRONT TORSION BAR SPRING (Independent Front Suspension)”

The FSM makes no distinction between actual method for removal and replacement (including re-indexing) of AHC versus non-AHC torsion bars but does assume, as @agaisin has highlighted and also as highlighted in multiple subsequent posts by other IH8MUD Members, that the Owner also is reviewing the relevant FSM sections in the drop-down menu headed

“ACTIVE HEIGHT CONTROL SYSTEM (Independent Front Suspension)”

and the sub-section labelled

“ON-VEHICLE INSPECTION”

Again, it is important to be aware of

• the different size and purpose of the torsion bars for AHC vehicles versus non-AHC vehicles (see also this link), and,
• the different hub-to-fender measurements for a stock AHC vehicle in standard condition, specifically, Front 19.75 inches, Rear 20.50 inches (or, Front 500 millimetres, Rear 520 miliimetres) – these approximations are widely and successfully used by IH8MUD members instead of the more finnicky measurements stated in the FSM, and,
• the different work required if a ‘lift’ is being undertaken on a vehicle fitted with AHC (search IH8MUD concerning ‘lifts’ – there are plenty of articles).

Although originally written for non-AHC vehicles and despite the differences from AHC vehicles, the longstanding detailed pictorial explanation by @Gunney also remains useful to all Owners of LC100 with IFS and AHC, and LX470 vehicles.

Nice link thank you

 

[TED the LX470]

Hello all,

I have recently purchased an LX 470 Australian delivered with 250,000 km or 155,000 miles on it. I am only the third owner from new, so over all the car is in pretty good shape. However i have what i would call a poor ride quality. I have read this entire thread and have had a crack at fixing a few things, i shall list below.

When i first purchased i did the low to high test and returned seven graduations on the AHC tank, this was with the car cross leveled, so new globes are needed.

Currently the car sits with these specs for heights measured from center of hub to bottom lip of fender

front left height 49 cm or 19.29 inch
front right height 49.5 cm or 19.48 inch
rear left height 52 cm or 20.5 inch
rear right height 52 cm or 20.5 inch

these measurements are close, however it would seem the front end is a little low.

techstream readings after new front globes installed and AHC fluid bleed, these were pulled from a wrecked 100 series sahara.

first in low

front right -1.9 inch
front left -1.9 inch
rear -1.5 inch

obviously pressures are zero as i connected to the car in low mode via techtsream, moved the car from L to N and got these readings.

front right -0.1 inch
front left 0.0 inch
rear -0.1 inch

front pressure 6.5 mpa
rear pressure 7.0 mpa

so as can be seen unless i'm a total bucket head the car should ride really well, large bumps are not an issue, however those smaller cracks and so on in the road seem to be quite harsh, others describe a buttery smooth ride. I can feel it at times, like the car wants to have a buttery smooth ride but at other times it simply is not. I have reduced my tire pressures all round to 32 psi to help things, but seemingly no "seat of the pants" measurable change.

The rear end of the car is however much softer than the front after globes and fluid change going over large speed bumps the front end is fine and the rear does sag a little, with a full tank of fuel.

I am wondering if re indexing my TB's and replacing the rear springs with the king's units as i am soon to be carrying extra weight around will improve things

 

[IndroCruise]

Hello all,

I have recently purchased an LX 470 Australian delivered with 250,000 km or 155,000 miles on it. I am only the third owner from new, so over all the car is in pretty good shape. However i have what i would call a poor ride quality. I have read this entire thread and have had a crack at fixing a few things, i shall list below.

When i first purchased i did the low to high test and returned seven graduations on the AHC tank, this was with the car cross leveled, so new globes are needed.

Currently the car sits with these specs for heights measured from center of hub to bottom lip of fender

front left height 49 cm or 19.29 inch
front right height 49.5 cm or 19.48 inch
rear left height 52 cm or 20.5 inch
rear right height 52 cm or 20.5 inch

these measurements are close, however it would seem the front end is a little low.

techstream readings after new front globes installed and AHC fluid bleed, these were pulled from a wrecked 100 series sahara.

first in low

front right -1.9 inch
front left -1.9 inch
rear -1.5 inch

obviously pressures are zero as i connected to the car in low mode via techtsream, moved the car from L to N and got these readings.

front right -0.1 inch
front left 0.0 inch
rear -0.1 inch

front pressure 6.5 mpa
rear pressure 7.0 mpa

so as can be seen unless i'm a total bucket head the car should ride really well, large bumps are not an issue, however those smaller cracks and so on in the road seem to be quite harsh, others describe a buttery smooth ride. I can feel it at times, like the car wants to have a buttery smooth ride but at other times it simply is not. I have reduced my tire pressures all round to 32 psi to help things, but seemingly no "seat of the pants" measurable change.

The rear end of the car is however much softer than the front after globes and fluid change going over large speed bumps the front end is fine and the rear does sag a little, with a full tank of fuel.

I am wondering if re indexing my TB's and replacing the rear springs with the king's units as i am soon to be carrying extra weight around will improve things

Late edits added to correct errors, typos and omissions!

G’day Ted the LX470,

Welcome to the Forum! It looks like you are getting a good handle on how the AHC system works – and it is a great system when it does work -- and like many of us or at least me, the learning process does involve ‘learning by frustration’.

Your post is informative – some comments are interpolated below.

1. Cross levelling and Operating Height measurements by tape

front left height 49 cm or 19.29 inch
front right height 49.5 cm or 19.48 inch
rear left height 52 cm or 20.5 inch
rear right height 52 cm or 20.5 inch

Hub to fender heights look reasonable compared to IH8MUD approximations for Front 19.75 inches or 500 millimetres and Rear 20.50 inches or 520 millimetres (as distinct from the attached finnicky Factory Service Manual - FSM - specifications), maybe you are a tad low at the front, presume you followed the required sequence:

(1) cross-levelled first with engine/AHC “OFF” using only Torsion Bar adjusters to obtain near as possible equal front hub-to-fender static heights to equalise loads on torsion bars, then,

(2) adjusted operating heights using only Height Control Sensor adjusters to increase/decrease vehicle height as required (measured with engine/AHC “ON”, but turn “OFF” for safety while making actual adjustments – easy for adjuster to slip while making adjustments, especially at rear, then vehicle may move suddenly if AHC is operating -- high potential for injury!)

Suggest always be religious about the different adjusters and their purposes. Frustration certainly follows when torsion bar adjusters are wrongly used to adjust height measurements instead of just equalise them (does not matter what the actual numbers are in that step), and/or, equally frustrating when the Height Control Sensor adjusters are wrongly used in an attempt to cross-level the front heights (already should have been equalised in the prior step – and cannot be done anyway by Height Control Sensor adjusters because Left Front AHC and Right front AHC are hydraulically connected and remain at equal pressure when steering is straight ahead – AHC is two channel system, “pumps up” Front and Rear, cannot “pump up” one front wheel in preference to the other).


2. Height Control Sensors

front right -0.1 inch
front left 0.0 inch
rear -0.1 inch

All close to zero, differences very small, readings look good but actual internal condition of Height Control Sensors is unknown without removal, inspection and testing of Sensors (see FSM and IH8MUD posts – this is not difficult).


3. AHC pressures

Presume AHC pressures measured with vehicle in standard condition on level surface, wheels straight ahead, all fuel tanks full, no persons nor freight nor temporary loads/fittings on board, temperature sensor disconnected at AHC Pump per FSM for Rear pressure reading.

front pressure: 6.5 Mpa (FSM-specified range: 6.4 to 7.4 MPa)
rear pressure: 7.0 Mpa (FSM-specified range: 5.6 to 6.7 MPa OR 5.9 to 7.0 Mpa if subtank fitted)

Height Accumulator pressure: unknown?? – expect around 10.5 MPa

It may be worth experimenting with slight increase in Front pressure to find ‘sweet spot’ for this vehicle, try 1 or 2 clockwise turns on both torsion bar adjusters to take pressures to 6.7 Mpa

Rear pressure is high, needs to come down for better damping:

OPTION #1: Replacement new genuine OEM stock springs plus 30 millimetre spacer plus possible airbags inside coils for infrequent variable heavy loads – this is a suitable solution if the duty of the vehicle is intended to be fairly light and the aim is to maintain best comfort from the AHC/TEMS system.

OR

OPTION #2: Replacement KING KTRS-79 springs – this is a suitable solution if the duty of the vehicle is more arduous and includes fitting substantial permanent or semi-permanent weight including a selection of: rear drawers, refrigerator, front bar, rear bar, sliders, roof rack and roof load, towball weight of camper/caravan, etc.

Explanation:

You could reduce rear AHC pressure by about 0.5 Mpa by adding 30 millimetre rear spring spacers at both sides and remove both third row seats for less than 0.5 Mpa reduction – but these small improvements do not seem worthwhile without replacement of stock rear OEM springs as well. The spacer causes deflection of the spring, thereby causing the spring to exert more force and carry more load at a given height setting, meaning that the rear AHC carries less load and is at lower pressure. This may give better damping at “N” height – but always take care – if there is too little AHC pressure, then damping actually will get worse and the vehicle may feel too ‘springy’. (NOTE: Replacing rear springs or adding rear spacers does not change rear vehicle height – that is controlled by the rear Height Control Sensor).

If your rear stock springs are original, they certainly are tired and past their best (meaning they have lost some of their ‘springyness’ – technically, they have lost some of their ‘spring rate’ (meaning the pounds of force per inch of spring deflection) has deteriorated.

The maximum load bearing capacity of the AHC system must not be exceeded – see second page of second attachment. The vehicle may sink to “LO” and may refuse to raise if overloaded. (By the way, be wary of the 3,260 kilogram GVM maximum allowable vehicle + contents weight limit in Australia for LC100 and LX470 without approved GVM Upgrade – which is close to impossible with the AHC/TEMS system).

The heavier duty alternative is to replace rear springs with KING KTRS-79 springs. These have a spring rate of about 130 pounds per inch of deflection which is about 37% higher than the spring rate of new stock AHC springs at 95 pounds per inch of deflection.

When KING KTRS-79 springs are fitted to an empty LC100 or LX470 which is not carrying any load, then the load share carried by the springs is too great, the load share carried by the rear AHC is much less than design, rear AHC pressure is too low (my personal experience was around 5.1Mpa initially), damping is greatly reduced and the rear is unacceptably ‘bouncy’.

For an Owner intending to load his/her vehicle with permanent or semi-permanent heavy fittings plus tow a trailer or campervan with a significant weight on the towball, plus carry passengers in the rear, the KING KTRS-79 springs are a good solution to avoid overloading the AHC system, keep the rear AHC pressure in the specified range and have the AHC/TEMS operating correctly in regard to height control and damping characteristics when weight is near GVM.

There are plenty of searchable posts about springs at IH8MUD. Here is a good post by uHu for some general insights about what happens at the limits of the TEMS part of the AHC/TEMS system.

It is mainly the TEMS system which is responsible for regulating the damping system in 16 steps continuously in real time and providing the comfort and ride quality -- see also the attachment to this message to obtain a clearer understanding of how this works.


4. Condition of AHC Gas Chambers a.k.a. ‘globes’ or ‘spheres’

Results of a current “HI/LO Test” is not reported.

To be comparable with FSM guidance, the “HI/LO Test” must be performed on a level surface with vehicle in standard condition, wheels straight ahead, all fuel tanks full, no persons nor freight nor temporary loads/fittings on board, at correct height and at correct AHC pressures.

For good AHC/TEMS performance, the ‘globes’ (called Gas Chambers in FSM) need to be in good condition – meaning that the “HI/LO Test” gives a good increase in graduations at the AHC Tank when the suspension is moved between “HI” and “LO” --- 14 graduations = excellent (globes are still near new); 7 graduations = poor (time to change ‘globes’). Actually, FSM says change ‘globes’ at 8 graduations in Australia – reason unknown!

Good AHC pressures within FSM-specified ranges tell NOTHING about ‘globe’ internal condition and tell NOTHING about the condition of individual ‘globes’.

Your observations include:

“…. new front globes installed and AHC fluid bleed, these were pulled from a wrecked 100 series sahara”.

“The rear end of the car is however much softer than the front after globes and fluid change going over large speed bumps the front end is fine and the rear does sag a little, with a full tank of fuel”.

The limitation of the “HI/LO Test” is that it can only measure total displacement of AHC fluid from all four ‘globes’ to the AHC tank, driven by the pressure of whatever nitrogen still remains on the gas side of the diaphragm in the ‘globes’. There is no method available which distinguishes the on-vehicle condition of individual ‘globes’. [Late edit: Maybe this is not quite correct -- the "16 Step Test" could reveal a problematic corner by a felt difference in stiffness -- but how to distinguish between a problem in a 'globe' from a problem in a Damping Force Control Actuator to which the 'globe' is attached?]

The condition of the replacement Front ‘globes’ second-hand from the mentioned wrecked Sahara is unknown unless you have reliable information from the previous Owner. (For non-Australians, the reference to Sahara is about the top-of-the-line LC100 model marketed with AHC in Australia from late-2005 until arrival of LC200 in 2007). If the replacement Front ‘globes’ were original on the source vehicle, they may be near their use-by date. I have a June 2006 Sahara and changed all four ‘globes’ Toyota OEM replacements at 8 graduations at 183,231 kilometres in May 2019 – admittedly a conservative decision made in advance of a long trip with vehicle weight close to allowable GVM. Now at 206,375 kilometres and 'globes' are still producing about 14 graduations at AHC tank -- as they should!

Your unchanged Rear ‘globes’ may be in suspect condition – and that will be difficult to ascertain. In the situation reported, it is quite possible for the replacement Front ‘globes’ to be in reasonable condition and able to displace sufficient AHC fluid in the “HI/LO Test” but mask inadequate condition of the Rear ‘globes’ displacing minimal AHC fluid in the test. Rear softness over bumps is consistent with Rear ‘globes’ past their best and incapable of providing adequate damping performance.

Late edit: Apparent softness (more like thumping) over bumps, especially at low speed, also may be a consequence of mechanical wear such as worn ball-joints, crumbling bushes at front and/or rear control arms, bushes at 'shock absorbers', bushes at swaybars (front and rear), front wheel bearings in need of repack and adjustment, etc.

The observation that ”….the rear does sag a little, with a full tank of fuel” also is a worry. This may be consistent with poor Rear ‘globe’ condition. Rear height is controlled by the Rear Height Control Sensor and not by the ‘globes’, so suspicion about the internal condition of this Sensor also arises.


The following conclusion is offered for consideration, subject to welcome comments from other IH8MUD Members:

1. The reported observations cause considerable doubts about conditions of current AHC ‘globes’ and a possible concern about the internal condition of the Rear Height Control Sensor, both of which need to be resolved,
2. If the concerns about 'globe' condition prove correct, then re-indexing torsion bars and replacing the rear springs with the King units will not correct the suspected conditions nor enhance performance, and, extra weight will make the situation worse,
3. If not already done, careful inspection of suspension and steering mechanical components may reveal opportunities for improvement and a quieter ride.

The recommended next step is become certain about good condition of front and rear ‘globes’ and front rear Height Control Sensors, and the condition of mechanical suspension components and linkages, especially if additional weight and long trips are being contemplated.

There may be other deeper problems in the AHC/TEMS systems but best to address the above matters first rather than speculate prematurely.

Happy for follow-up by ongoing posts or PM if that helps.

 

[IndroCruise]

Late edits added to correct errors, typos and omissions!

G’day Ted the LX470,

Welcome to the Forum! It looks like you are getting a good handle on how the AHC system works – and it is a great system when it does work -- and like many of us or at least me, the learning process does involve ‘learning by frustration’.

Your post is informative – some comments are interpolated below.

1. Cross levelling and Operating Height measurements by tape

front left height 49 cm or 19.29 inch
front right height 49.5 cm or 19.48 inch
rear left height 52 cm or 20.5 inch
rear right height 52 cm or 20.5 inch

Hub to fender heights look reasonable compared to IH8MUD approximations for Front 19.75 inches or 500 millimetres and Rear 20.50 inches or 520 millimetres (as distinct from the attached finnicky Factory Service Manual - FSM - specifications), maybe you are a tad low at the front, presume you followed the required sequence:

(1) cross-levelled first with engine/AHC “OFF” using only Torsion Bar adjusters to obtain near as possible equal front hub-to-fender static heights to equalise loads on torsion bars, then,

(2) adjusted operating heights using only Height Control Sensor adjusters to increase/decrease vehicle height as required (measured with engine/AHC “ON”, but turn “OFF” for safety while making actual adjustments – easy for adjuster to slip while making adjustments, especially at rear, then vehicle may move suddenly if AHC is operating -- high potential for injury!)

Suggest always be religious about the different adjusters and their purposes. Frustration certainly follows when torsion bar adjusters are wrongly used to adjust height measurements instead of just equalise them (does not matter what the actual numbers are in that step), and/or, equally frustrating when the Height Control Sensor adjusters are wrongly used in an attempt to cross-level the front heights (already should have been equalised in the prior step – and cannot be done anyway by Height Control Sensor adjusters because Left Front AHC and Right front AHC are hydraulically connected and remain at equal pressure when steering is straight ahead – AHC is two channel system, “pumps up” Front and Rear, cannot “pump up” one front wheel in preference to the other).


2. Height Control Sensors

front right -0.1 inch
front left 0.0 inch
rear -0.1 inch

All close to zero, differences very small, readings look good but actual internal condition of Height Control Sensors is unknown without removal, inspection and testing of Sensors (see FSM and IH8MUD posts – this is not difficult).


3. AHC pressures

Presume AHC pressures measured with vehicle in standard condition on level surface, wheels straight ahead, all fuel tanks full, no persons nor freight nor temporary loads/fittings on board, temperature sensor disconnected at AHC Pump per FSM for Rear pressure reading.

front pressure: 6.5 Mpa (FSM-specified range: 6.4 to 7.4 MPa)
rear pressure: 7.0 Mpa (FSM-specified range: 5.6 to 6.7 MPa OR 5.9 to 7.0 Mpa if subtank fitted)

Height Accumulator pressure: unknown?? – expect around 10.5 MPa

It may be worth experimenting with slight increase in Front pressure to find ‘sweet spot’ for this vehicle, try 1 or 2 clockwise turns on both torsion bar adjusters to take pressures to 6.7 Mpa

Rear pressure is high, needs to come down for better damping:

OPTION #1: Replacement new genuine OEM stock springs plus 30 millimetre spacer plus possible airbags inside coils for infrequent variable heavy loads – this is a suitable solution if the duty of the vehicle is intended to be fairly light and the aim is to maintain best comfort from the AHC/TEMS system.

OR

OPTION #2: Replacement KING KTRS-79 springs – this is a suitable solution if the duty of the vehicle is more arduous and includes fitting substantial permanent or semi-permanent weight including a selection of: rear drawers, refrigerator, front bar, rear bar, sliders, roof rack and roof load, towball weight of camper/caravan, etc.

Explanation:

You could reduce rear AHC pressure by about 0.5 Mpa by adding 30 millimetre rear spring spacers at both sides and remove both third row seats for less than 0.5 Mpa reduction – but these small improvements do not seem worthwhile without replacement of stock rear OEM springs as well. The spacer causes deflection of the spring, thereby causing the spring to exert more force and carry more load at a given height setting, meaning that the rear AHC carries less load and is at lower pressure. This may give better damping at “N” height – but always take care – if there is too little AHC pressure, then damping actually will get worse and the vehicle may feel too ‘springy’. (NOTE: Replacing rear springs or adding rear spacers does not change rear vehicle height – that is controlled by the rear Height Control Sensor).

If your rear stock springs are original, they certainly are tired and past their best (meaning they have lost some of their ‘springyness’ – technically, they have lost some of their ‘spring rate’ (meaning the pounds of force per inch of spring deflection) has deteriorated.

The maximum load bearing capacity of the AHC system must not be exceeded – see second page of second attachment. The vehicle may sink to “LO” and may refuse to raise if overloaded. (By the way, be wary of the 3,260 kilogram GVM maximum allowable vehicle + contents weight limit in Australia for LC100 and LX470 without approved GVM Upgrade – which is close to impossible with the AHC/TEMS system).

The heavier duty alternative is to replace rear springs with KING KTRS-79 springs. These have a spring rate of about 130 pounds per inch of deflection which is about 37% higher than the spring rate of new stock AHC springs at 95 pounds per inch of deflection.

When KING KTRS-79 springs are fitted to an empty LC100 or LX470 which is not carrying any load, then the load share carried by the springs is too great, the load share carried by the rear AHC is much less than design, rear AHC pressure is too low (my personal experience was around 5.1Mpa initially), damping is greatly reduced and the rear is unacceptably ‘bouncy’.

For an Owner intending to load his/her vehicle with permanent or semi-permanent heavy fittings plus tow a trailer or campervan with a significant weight on the towball, plus carry passengers in the rear, the KING KTRS-79 springs are a good solution to avoid overloading the AHC system, keep the rear AHC pressure in the specified range and have the AHC/TEMS operating correctly in regard to height control and damping characteristics when weight is near GVM.

There are plenty of searchable posts about springs at IH8MUD. Here is a good post by uHu for some general insights about what happens at the limits of the TEMS part of the AHC/TEMS system.

It is mainly the TEMS system which is responsible for regulating the damping system in 16 steps continuously in real time and providing the comfort and ride quality -- see also the attachment to this message to obtain a clearer understanding of how this works.


4. Condition of AHC Gas Chambers a.k.a. ‘globes’ or ‘spheres’

Results of a current “HI/LO Test” is not reported.

To be comparable with FSM guidance, the “HI/LO Test” must be performed on a level surface with vehicle in standard condition, wheels straight ahead, all fuel tanks full, no persons nor freight nor temporary loads/fittings on board, at correct height and at correct AHC pressures.

For good AHC/TEMS performance, the ‘globes’ (called Gas Chambers in FSM) need to be in good condition – meaning that the “HI/LO Test” gives a good increase in graduations at the AHC Tank when the suspension is moved between “HI” and “LO” --- 14 graduations = excellent (globes are still near new); 7 graduations = poor (time to change ‘globes’). Actually, FSM says change ‘globes’ at 8 graduations in Australia – reason unknown!

Good AHC pressures within FSM-specified ranges tell NOTHING about ‘globe’ internal condition and tell NOTHING about the condition of individual ‘globes’.

Your observations include:

“…. new front globes installed and AHC fluid bleed, these were pulled from a wrecked 100 series sahara”.

“The rear end of the car is however much softer than the front after globes and fluid change going over large speed bumps the front end is fine and the rear does sag a little, with a full tank of fuel”.

The limitation of the “HI/LO Test” is that it can only measure total displacement of AHC fluid from all four ‘globes’ to the AHC tank, driven by the pressure of whatever nitrogen still remains on the gas side of the diaphragm in the ‘globes’. There is no method available which distinguishes the on-vehicle condition of individual ‘globes’. [Late edit: Maybe this is not quite correct -- the "16 Step Test" could reveal a problematic corner by a felt difference in stiffness -- but how to distinguish between a problem in a 'globe' from a problem in a Damping Force Control Actuator to which the 'globe' is attached?]

The condition of the replacement Front ‘globes’ second-hand from the mentioned wrecked Sahara is unknown unless you have reliable information from the previous Owner. (For non-Australians, the reference to Sahara is about the top-of-the-line LC100 model marketed with AHC in Australia from late-2005 until arrival of LC200 in 2007). If the replacement Front ‘globes’ were original on the source vehicle, they may be near their use-by date. I have a June 2006 Sahara and changed all four ‘globes’ Toyota OEM replacements at 8 graduations at 183,231 kilometres in May 2019 – admittedly a conservative decision made in advance of a long trip with vehicle weight close to allowable GVM. Now at 206,375 kilometres and 'globes' are still producing about 14 graduations at AHC tank -- as they should!

Your unchanged Rear ‘globes’ may be in suspect condition – and that will be difficult to ascertain. In the situation reported, it is quite possible for the replacement Front ‘globes’ to be in reasonable condition and able to displace sufficient AHC fluid in the “HI/LO Test” but mask inadequate condition of the Rear ‘globes’ displacing minimal AHC fluid in the test. Rear softness over bumps is consistent with Rear ‘globes’ past their best and incapable of providing adequate damping performance.

Late edit: Apparent softness (more like thumping) over bumps, especially at low speed, also may be a consequence of mechanical wear such as worn ball-joints, crumbling bushes at front and/or rear control arms, bushes at 'shock absorbers', bushes at swaybars (front and rear), front wheel bearings in need of repack and adjustment, etc.

The observation that ”….the rear does sag a little, with a full tank of fuel” also is a worry. This may be consistent with poor Rear ‘globe’ condition. Rear height is controlled by the Rear Height Control Sensor and not by the ‘globes’, so suspicion about the internal condition of this Sensor also arises.


The following conclusion is offered for consideration, subject to welcome comments from other IH8MUD Members:

1. The reported observations cause considerable doubts about conditions of current AHC ‘globes’ and a possible concern about the internal condition of the Rear Height Control Sensor, both of which need to be resolved,
2. If the concerns about 'globe' condition prove correct, then re-indexing torsion bars and replacing the rear springs with the King units will not correct the suspected conditions nor enhance performance, and, extra weight will make the situation worse,
3. If not already done, careful inspection of suspension and steering mechanical components may reveal opportunities for improvement and a quieter ride.

The recommended next step is become certain about good condition of front and rear ‘globes’ and front rear Height Control Sensors, and the condition of mechanical suspension components and linkages, especially if additional weight and long trips are being contemplated.

There may be other deeper problems in the AHC/TEMS systems but best to address the above matters first rather than speculate prematurely.

Happy for follow-up by ongoing posts or PM if that helps.

Hi @TED the LX470,

In my earlier reply – and please note that there were few late edits made for clarity including one a few moments ago – I wrote that

“There may be other deeper problems in the AHC/TEMS systems but best to address the above matters first rather than speculate prematurely”.

On the assumption that you have satisfied yourself concerning the matters raised in the conclusion my earlier reply, it now may be a good time to give an indication of what those “deeper problems” may be and also suggest where some further information might be found.

Your original post included the statement that

“…. large bumps are not an issue, however those smaller cracks and so on in the road seem to be quite harsh, others describe a buttery smooth ride. I can feel it at times, like the car wants to have a buttery smooth ride but at other times it simply is not”.

Similar observations and frustrations are scattered through a range of posts in various IH8MUD threads. Several important threads come to mind when others were dealing with similar experiences. These threads are worth reading in their entirety.

In the thread at the following link

AHC does large accumulator affect damping?

there is an exchange from early 2014 between @cruiser03 and @PADDO and @uHu (both very knowledgeable) and several other Members. It results in a conclusion by @cruiser03 at post #22 in this thread that

“Here are my findings in regards to the AHC riding harshly over small bumps: At least 3 of my 4 AHC dampeners failed and one was marginal”.

(“Dampeners” means the Damping Force Control Actuators – the device to which the Gas Chambers a.k.a. ‘globes’ are attached).

Some issues and tests from the Factory Service Manual (FSM) are described, including the “16 Step Test” which aims to identify problems at each corner of the vehicle, and also, testing of the resistances of the circuits in the Damping Force Control Actuators as an indicator of their health. The idea is to try to separate common problems arising from poor ‘globe’ condition from more obscure problems arising from faults in the Damping Force Control Actuators. I have personally used the “16 Step Test” but I have not yet gone further and tested the resistances in the Damping Force Control Actuators – does not seem difficult with a decent multimeter.

There is some further discussion on a range of matters in the next following link which also is worth reading in it entirety:

Suspension problem even after replacing almost everything

All of that said, using the IH8MUD Search function will reveal a lot of information and contributions by IH8MUD Members -- and this a fantastic resource -- but it may need to be accompanied by a systematic approach.

Attached is an extract of the entire AHC Diagnostic section of the FSM – this runs for about 118 pages from a total of 5,988 pages in a consolidated version of the FSM.

This seems a bit daunting and some of the circuit diagrams are a bit dazzling.

To cut to the chase, it is worth a look at the PROBLEMS SYMPTOMS TABLE at Page 19. This Table gives an idea of what symptom relates to what problem (or problems).

Other useful pages also are listed below – the page numbers are the attached PDF page numbers.

Page 1 – TROUBLE SHOOTING FLOW DIAGRAM


Page 4 – PRE-CHECK (starts at FSM Page DI-208)
This section contains some basic checks.

For example, scroll down to page 9 and sub-section 4. DAMPING CONDITION CHECK . This often is referred to as the “16 Step Test” in IH8MUD posts and describes how to check the progressive stiffness of the step motors in the Damping Force Control Actuators through the 16 steps. This check is made separately at each corner of the vehicle. To go further, the resistances of the circuits in the Damping Force Control Actuators can be checked as described at page 40 in the section headed “Damping Force Control Actuator Circuit”.

See also at page 10 the sub-section 5 . HEIGHT CONTROL OPERATION (ACTIVE TEST). This test is mentioned often in IH8MUD posts, for example in relation to the “Active Test” required as a method to restart the AHC Pump if the AHC tank has emptied and the AHC pump stops after entraining air while bleeding AHC fluid.

Page 11 – DIAGNOSTIC TROUBLE CODE CHART

Page 15 – PARTS LOCATION

Page 19 - PROBLEM SYMPTOMS TABLE

The following examples are offered to illustrate how this part of the FSM works ….


Page 22 – HEIGHT CONTROL SENSOR CIRCUIT
Note description of “Fail safe function”:
“If a trouble occurs in the height control sensor circuit, the height control is prohibited after the ECU has adjusted the vehicle height to the standard (fluid pressure correspond to the standard height)”.
In this condition, you will not get a smooth ride.

Other conditions also can cause a ‘fail-safe’ response – sometimes simple, like widely different Height Control Sensor outputs or other conflicting signals from other sensors, or sometimes the cause arises from a deeper (and usually rarer) component problem. Not always does a scan reveal helpful Diagnostic Trouble Codes (DTC's) and so the Problem Symptoms Table and the knowledge of other IH8MUD Members can be very helpful.

Page 24 – Check output value of height control sensor
(In these descriptions "Handheld" can mean Techstream and a laptop or some other scanner).

Page 25 – Check height control sensor
(Also see diagrams here. The FSM method uses 3 x 1.5 Volt AA or AAA cells to simulate input voltage applied to the sensor when in the vehicle and then specifies the output Voltage at the Height Control Sensor potentiometer at a range of angles which in turn correspond to a range of heights. The output Voltage is the signal read by the ECU unit which in turn determines actions by the AHC system. In an earlier post in this thread, uHu has described some very helpful ‘health checks’ of the Height Control Sensors by measuring resistance in Ohms rather than measuring potentiometer output Voltages. This is very handy -- needs only a multimeter and does not require the FSM battery arrangement. The diagrams on page 25 show the terminal numbers mentioned by uHu).

Page 38 – Damping Force Control Actuator Circuit
This section describes a range of fault conditions in this circuit (at each such actuator). “The AHC Electronic Control Unit (ECU) sends a signal to damping force control actuator to drive the rotary valve of the shock absorber changing the shock absorber damping force. The actuator is driven electromagnetically by step motor so that it can accurately follow the driving conditions that change frequently”.

At page 40, a health check is described which involves measuring the resistances of the circuits in the Damping Force Control Actuators. Further detail is given in the IH8MUD posts referenced above.

Note the description of this “Fail-safe function”:
“If trouble occurs in the front or rear wheel damping force control actuator circuit, ECU prohibits the damping force control after the ECU has returned the damping force of the other side wheel to the normal condition”.

In this condition you will not get a smooth ride. See also sub-section 4. DAMPING CONDITION CHECK as mentioned above.

…. and so this FSM Extract goes on to describe other parts of the AHC/TEMS systems, relevant checks, possible fault conditions, Diagnostic Trouble Codes a.k.a. DTC's (although these may not always appear in a scanner) and the ‘fail-safe’ modes and symptoms which may be experienced.

Another FSM source can be found at https://lc100e.github.io/manual/. This provides details relevant to particular LC100 models, year of manufacture, and country of destination. Very useful. It also is relevant to most parts of LX470 models of similar years and is particularly relevant to the AHC/TEMS systems.

Hope this helps. Please post any impressions, progress and updates or outcomes so that we all can learn.

 

[TED the LX470]

Hi, @IndroCruise

You my friend are an absolute freaking legend. Thank you very much for the information that you have so far provided.

From reading your very informative previous reply's i have come to the following process pathway to fix my issue. I however will state that my aim is to provide a problem free base from that i can work from ie install bullbar rear draws and so on, i see no point in trying to work backwards loading my car with loads of aftermarket equipment and then having AHC issues and then trying to rectify the new problems. I figure fix the base line problem first, gain an understanding on how the system works in doing said fix, then build on that and keeping in mind vehicle limitations, with regard AHC. So now to my process.

1 - obtain the rear set of globes from donor car........... this would mean a replacement cost of $440 for the complete set of four, i do know and realize this maybe a short term solution, but it is a gamble at this time i am happy to take, given the current climate economically.

2 - install rear globes and re bleed the system........... the overall vehicle damping and ride quality particularly in the rear should improve, even with current stock rear springs, pressures will still be a bit high in the rear, but for the moment i can deal with that.

3 - cross level the car again, this time adjusting the front height control sensors to obtain perfect heights as per Ih8 center hub to fender specs, with fluid temp censor disconnected (for correct rear pressure reading)

4 - test drive the car over a couple of days.... over repeat sections of road (test loop) to gauge the changes in ride quality, adjust the TEMS switch etc

The above should give me something to work with and i should see a marked improvement in ride quality. If however a marked improvement is not gained proceed with the following.

5 - perform the 16 step test and also measure the ohms resistance of the stepper motors, to establish if one or more of the damper control actuators are faulty. Check cables, plugs/connectors both male and female from AHC computer and at all damper control actuators. replace or fix/clean as required

6 - clean and inspect the ride height control censors, check cables and connectors,rebuild or replace as required,

7 - pull up techstream and make sure that all censor inputs to the AHC computer are working correctly and feeding legitimate information, ride height, steering angle etc if it's an input test and inspect it. replace or fix/clean as required.

8 - test all of the switching solenoid functions via techstream and listen for the familiar clicking solenoid sound.

9 - reset AHC computer

10 - new AHC computer

11 - new tires ( are needed regardless)

12 - replace any worn suspension ball joints, bearings, bushes etc

points 1 through 9 are low cost
points 10 through 12 are higher in cost

What i am confident i can eliminate completely at this point are the two following items

1 - AHC pump, it is quiet and the car will rise from low to high in 32 seconds, so not an issue at the moment
2 - ride height accumulator as i see 10.4 - 10.5 mpa in techstream consistently and as the car rises from low to high in 32 seconds again not an issue at the moment

What i have noted in the last two days

The car in an as is un changed condition ie AHC bleed, cross level and getting front pressures down and replacing the front globes with new, be it secondhand items as per my first post, is nothing short of miraculous. I would say a 75% improvement in overall ride quality. I know i stated the other day that i have seen "no real improvement" or the ride "seems to come and go, like it wants to give a good ride" but i sure do now......... that buttery smooth ride is seemingly returning all buy its self, it is not perfect but it is a dam huge improvement. I can only think of the following reasons.

1 - the new AHC fluid has been able to penetrate the ride control actuators/pump and re lubricate the internals of with a new film of lubricant as now when turning the TEMS switch rather than going from harsh to teeth shattering, it now goes from buttery smooth with the occasional harsh bump to firmer with a few extra harsh bumps thrown in the mix. Others have reported after a fluid change a improvement in ride also.

2 - the ride improves as speed increases particularly above 75-80 km/hr or so with the TEMS switch set at full soft. (have not tried other settings on my test loop as yet)

3 - under braking the car does not dip as much as it once did, in fact the overall brake performance has lifted, however the car seems to roll in corners more so,

4 - the car seems to have a hole in the ride quality improvement between 40-70 km/h below and above these speeds it has improved immensely


I am happy to report that progress has been made. now to make it awesome

thanks again @IndroCruise

 

[spaber05]

Just stopping by to confirm what everyone in here already knew. Swapped out the front left height sensor and everything is peachy. I haven't gotten around to plugging in to check neutral pressures, but everything rides like a dream so I can't imagine things are way off, especially since I just recently dialed things in. Thanks @PADDO, @IndroCruise, and @uHu for the input!

 

[IndroCruise]

Hi, @IndroCruise

You my friend are an absolute freaking legend. Thank you very much for the information that you have so far provided.

From reading your very informative previous reply's i have come to the following process pathway to fix my issue. I however will state that my aim is to provide a problem free base from that i can work from ie install bullbar rear draws and so on, i see no point in trying to work backwards loading my car with loads of aftermarket equipment and then having AHC issues and then trying to rectify the new problems. I figure fix the base line problem first, gain an understanding on how the system works in doing said fix, then build on that and keeping in mind vehicle limitations, with regard AHC. So now to my process.

1 - obtain the rear set of globes from donor car........... this would mean a replacement cost of $440 for the complete set of four, i do know and realize this maybe a short term solution, but it is a gamble at this time i am happy to take, given the current climate economically.

2 - install rear globes and re bleed the system........... the overall vehicle damping and ride quality particularly in the rear should improve, even with current stock rear springs, pressures will still be a bit high in the rear, but for the moment i can deal with that.

3 - cross level the car again, this time adjusting the front height control sensors to obtain perfect heights as per Ih8 center hub to fender specs, with fluid temp censor disconnected (for correct rear pressure reading)

4 - test drive the car over a couple of days.... over repeat sections of road (test loop) to gauge the changes in ride quality, adjust the TEMS switch etc

The above should give me something to work with and i should see a marked improvement in ride quality. If however a marked improvement is not gained proceed with the following.

5 - perform the 16 step test and also measure the ohms resistance of the stepper motors, to establish if one or more of the damper control actuators are faulty. Check cables, plugs/connectors both male and female from AHC computer and at all damper control actuators. replace or fix/clean as required

6 - clean and inspect the ride height control censors, check cables and connectors,rebuild or replace as required,

7 - pull up techstream and make sure that all censor inputs to the AHC computer are working correctly and feeding legitimate information, ride height, steering angle etc if it's an input test and inspect it. replace or fix/clean as required.

8 - test all of the switching solenoid functions via techstream and listen for the familiar clicking solenoid sound.

9 - reset AHC computer

10 - new AHC computer

11 - new tires ( are needed regardless)

12 - replace any worn suspension ball joints, bearings, bushes etc

points 1 through 9 are low cost
points 10 through 12 are higher in cost

What i am confident i can eliminate completely at this point are the two following items

1 - AHC pump, it is quiet and the car will rise from low to high in 32 seconds, so not an issue at the moment
2 - ride height accumulator as i see 10.4 - 10.5 mpa in techstream consistently and as the car rises from low to high in 32 seconds again not an issue at the moment

What i have noted in the last two days

The car in an as is un changed condition ie AHC bleed, cross level and getting front pressures down and replacing the front globes with new, be it secondhand items as per my first post, is nothing short of miraculous. I would say a 75% improvement in overall ride quality. I know i stated the other day that i have seen "no real improvement" or the ride "seems to come and go, like it wants to give a good ride" but i sure do now......... that buttery smooth ride is seemingly returning all buy its self, it is not perfect but it is a dam huge improvement. I can only think of the following reasons.

1 - the new AHC fluid has been able to penetrate the ride control actuators/pump and re lubricate the internals of with a new film of lubricant as now when turning the TEMS switch rather than going from harsh to teeth shattering, it now goes from buttery smooth with the occasional harsh bump to firmer with a few extra harsh bumps thrown in the mix. Others have reported after a fluid change a improvement in ride also.

2 - the ride improves as speed increases particularly above 75-80 km/hr or so with the TEMS switch set at full soft. (have not tried other settings on my test loop as yet)

3 - under braking the car does not dip as much as it once did, in fact the overall brake performance has lifted, however the car seems to roll in corners more so,

4 - the car seems to have a hole in the ride quality improvement between 40-70 km/h below and above these speeds it has improved immensely


I am happy to report that progress has been made. now to make it awesome

thanks again @IndroCruise

Seems like you are well across the issues and have actions in a good sequence -- hope all goes well and more improvement follows! Suggest a "HI/LO Test" to check graduations at the AHC Tank around Step 4 in the first list in your reply -- probably you already have this in mind after adding donor rear 'globes' ex Sahara. This easy-to-do test helps you observe the overall condition of 'globes' and gives you a new baseline. Good to do this test before and after 'globe' changes so as to monitor improvements -- although as you mention, 'ride quality' on a 'test circuit' is the ultimate test. Separately, be wary of high pressures which will affect damping and challenge seals throughout the AHC system, especially at shock absorber struts -- but you are across the options for dealing with such situations.

If not already seen, https://lc100e.github.io/manual/ provides good access to a full Factory Workshop Manual. This applies to LC100 rather than LX470 but covers the many similar systems and components which are common to both lines of vehicles.

If not already done, membership of the Australian site LCOOL.org :: Index also is worthwhile although not as extensive as IH8MUD. LCOOL is free but registration is required -- it provides posts about local experiences and information including links to various manuals.

Go well!!

 

[JJ_SC]

I'm not sure where to post this question but this thread seems to cover everything AHC so here it is...

At what pressure does the system turn itself off?

I ask because when I head out for a family off-road trip, I tend to overload the truck. I've got king springs and spacers and the whole deal. But, also, 2 teenagers and 4 mt bikes and a dissent rear bumper... and the dog. And a boat. And the list goes on and on. But, I'm wondering if I can check the AHC pressures as I pack and, once I get to a certain point, just know that my daughter's boyfriend can no longer be put in the car because he's too heavy.

Of course, I can add weight and check until it shuts off. But I'm wondering if anyone knows the answer already.

Thanks!

 

[silver02accord]

I've got the heights even with AHC OFF and engine OFF. It seems when I fire up AHC into normal mode, drive around etc and remeasure the front right fender is 0.25inch higher than the front left fender. As I understand it I need to adjust the height sensor on the front right fender and get the two sides even(in this case 19.625 would be in line with the left side). I didn't want to mess with the height sensors as it was close enough to 19.75 but I don't want it riding tilted either, even if only 0.25 if I can correct it. With these numbers my ICarsoft is reading FR Height Control Sensor 0.024 inch and FL Height Control Sensero -0.087 inch. Rear is 0.236 inch. Pressure front is 6.6 and pressure rear is 6.7.

Is there any sense in pulling the ahc sensor connector back and inspecting and cleaning them or is it best practice to not mess with them if I do not absolutely have to?

Very happy with the results I've got from everyone on here, just looking to put the icing on the cake.

 

[ramangain]

@silver02accord ever heard the difference between a physicist and engineer?

An engineer will be given a spec, meet it, and move to the next task.
A physicist reads spec as "special"; meaning if he/she can exceed it, it must be special enough to publish in some esoteric journal.

Which are you?

 

[silver02accord]

@silver02accord ever heard the difference between a physicist and engineer?

An engineer will be given a spec, meet it, and move to the next task.
A physicist reads spec as "special"; meaning if he/she can exceed it, it must be special enough to publish in some esoteric journal.

Which are you?

Hahahah! I'm still trying to figure that out

 

[IndroCruise]

I've got the heights even with AHC OFF and engine OFF. It seems when I fire up AHC into normal mode, drive around etc and remeasure the front right fender is 0.25inch higher than the front left fender. As I understand it I need to adjust the height sensor on the front right fender and get the two sides even(in this case 19.625 would be in line with the left side). I didn't want to mess with the height sensors as it was close enough to 19.75 but I don't want it riding tilted either, even if only 0.25 if I can correct it. With these numbers my ICarsoft is reading FR Height Control Sensor 0.024 inch and FL Height Control Sensero -0.087 inch. Rear is 0.236 inch. Pressure front is 6.6 and pressure rear is 6.7.

Is there any sense in pulling the ahc sensor connector back and inspecting and cleaning them or is it best practice to not mess with them if I do not absolutely have to?

Very happy with the results I've got from everyone on here, just looking to put the icing on the cake.

The results for your vehicle seems to be "within tolerances" and so I agree with @ramangain but maybe that is prejudiced by my engineering background! In short, pursuit of perfection in scanner numbers may not overcome the inherent variations caused by many unavoidable 'imperfections' -- such as slightly unequal wear and tear or deformation in Height Control Sensors or even in mechanical suspension parts such as control arms, bushes, ball-joints, bearings, tires, etc which may affect how the chassis 'sits' on the suspension. Another thought is that nothing manufactured is ever 'exact' -- there is always some degree of variation which is expected by the designer and is 'tolerable' while maintaining the designed functionality. Personally, I generally would encourage removal and external, internal and electrical examination of Height Control Sensors at some point depending on operating conditions because they are out of sight, out of mind, unloved and easily overlooked. Yet they operate in one of the most hostile underbody environments on the vehicle -- subject to sticks, stones, mud, water, snow, salt, heat, cold, humidity etc -- and yet the AHC ECU and the AHC/TEMS operation relies heavily on the signals these Sensors send. There are the usual consequences of a fault condition causing "garbage in = garbage out" -- which one day may result in some form of "fail safe" mode being experienced. Does that mean you need to pull them now? That has to be your decision. It is worthwhile keeping the Height Control Sensors under watch.