Definitive list of AHC maintenance items (3 Viewers)

[PabloCruise]

I contacted kings to get their official specs on the rear ahc springs

The KTRS-79 are a linear rate coil 130lb in rate. 430mm free height and 14.5mm wire.

I installed some King springs today - so far, so good.

King Springs AHC KTRS-79

My big problem now is that I had to re-install Techstream (long story, my wife's dog peed in my old computer and it died)

Now when I start Techstream, it asks me for a key. It do not think it did the first time. Has anyone else encountered this?

 

[SAMTHEMAN]

An AHC related TSB attached. Contains an exploded view of the AHC pump, and info about production date of the height control accumulator.
Informs of a possible cause of ahc pump malfunction.

Dear uHu

I am new to this forum and this is my first post

I have a 2004 Land cruiser VX limited Japanese version
I have installed Techstream and have got the Xhorse cable
The cable and techstream has access to all the ECUs but the AHC is not communicating or connecting.
I tried it several times with many location options and Year Codes

Can some one give me some advise

 

[uHu]

Welcome to the forum, Sam.
If the AHC ECU is otherwise working, I would look at how the TechStream connects. Iirc, there are couple of signalling options.
If the ECU does not do it's job with the AHC, I would check the ECU and connectors.

Samtheman -- Where you a fan of Nihal, the saxophonist? (RIP)

 

[SAMTHEMAN]

Welcome to the forum, Sam.
If the AHC ECU is otherwise working, I would look at how the TechStream connects. Iirc, there are couple of signalling options.
If the ECU does not do it's job with the AHC, I would check the ECU and connectors.

Samtheman -- Where you a fan of Nihal, the saxophonist? (RIP)

Dear uHu
Nihal is one artist I loved..

may he rest in peace


back to business

I have shorted the pins of the DLC1 as described above in this thread and checked.
all the inputs to the AHC ECU was OK

The OFF light sequences
the brakes
the door courtesy
the 20 kmph threshold
the up down functions


the Damper controls also I feel very well the 4 position switch responses are very clear and sensed

my only issue is the Techstream says the ECU is not available or not communicating only for the AHC ECU

Can you explain me

''I would look at how the TechStream connects. Iirc, there are couple of signalling options.''

my vehicle is a japanese version 2004 LC100

I want to check the AHC pressures and adjust the TBs and the Rear coil spacers....

 

[PADDO]

Sam
When you connect Techstream to your vehicle what vehicle year/models are offered? Try different configurations as Techstream isn't 100% intuitive and doesn't fully auto detect the vehicle's actual configuration and therefore may not allow access to the correct look up tables. For example if you connect to an LX (with its standard AHC) but select LC (for North America - AHC in limited years only) from the vehicles offered then you can't access AHC - change vehicle to LX and it then recognizes the AHC ECU for full testing functionality. There are so many releases of pirated Techstream with x Horse that there likely isn't a definitive answer however. I use a version 7 copy of Techstream and on connection to my vehicle it senses the model year but wants to know if it's an LX or GX as the only two options.
Additionally, your JPN vehicle may have a different interface protocol to others as different world regions have different interface standards that evolve over the years. In Techstream try the cable check utility and confirm what lines to the DLC are active. You want Pin 7 (SIL) active for correct interfacing, at least that's a requirement for the North America interface protocol. Lastly, there are several x Horse driver interfaces and the newer release (iirc) may not connect properly with model year 05+, at least for North America vehicles, so there's potentially some VCI vagaries too.
HTH

 

[SAMTHEMAN]

Sam
When you connect Techstream to your vehicle what vehicle year/models are offered? Try different configurations as Techstream isn't 100% intuitive and doesn't fully auto detect the vehicle's actual configuration and therefore may not allow access to the correct look up tables. For example if you connect to an LX (with its standard AHC) but select LC (for North America - AHC in limited years only) from the vehicles offered then you can't access AHC - change vehicle to LX and it then recognizes the AHC ECU for full testing functionality. There are so many releases of pirated Techstream with x Horse that there likely isn't a definitive answer however. I use a version 7 copy of Techstream and on connection to my vehicle it senses the model year but wants to know if it's an LX or GX as the only two options.
Additionally, your JPN vehicle may have a different interface protocol to others as different world regions have different interface standards that evolve over the years. In Techstream try the cable check utility and confirm what lines to the DLC are active. You want Pin 7 (SIL) active for correct interfacing, at least that's a requirement for the North America interface protocol. Lastly, there are several x Horse driver interfaces and the newer release (iirc) may not connect properly with model year 05+, at least for North America vehicles, so there's potentially some VCI vagaries too.
HTH

Dear PADDO
Thanks for coming forward to help me

for the last few weeks I kept on reading this forum and learnt a lot from you and UHU and a few more people
I have seen you and them coming forward to help people like us and you are great pillars of strength to all of us..
I have almost tried every thing you suggested
the year
the region
the LX and LC

all the ECU s other than AHC is accessible and even I could read codes and do some changes like the Tilt and Telescopic cancellation etc

The Japan Region Techstream does not show an AHC(although the japanese domestic modle I own has it mounted)

Europe North America and other regions Techstream has the AHC Ecu shown but you cannot access it

tommorrow I will do teh Cable check as you said(its almost midnight)I will update you the results



SOME TECHNICAL CLARIFICATION

In AHC modles the vehicle weight is carried by the mechanical springs and the hydraulic Rams

If the height sensors are adjusted and the vehicle height is raised the weight to be carried by the hydraulic should increase.
To proportion the weight properly (at the new height) the front TBs has to be cranked and the rear spring may be fitted with a spacer

with out doing the required to the TBs and Coil Springs at rear if the height is increased , can the higher pressure of AHC keep the accumulator diaphragms pressed in, so that the shocks will not have accumulator space for the damping?


I have raised my vehicle height by about 2 inches approx by sensor adjustments and the ride got stiffer specially in rear..
Front is little softer after a few turns of the TBs..


Is it correct what I think?

further AHC shocks--- what are they really??
Real shocks or some Hyd Rams with the damping chamber in the accumulators?

 

[PADDO]

If you can read DTCs, adjust user settings etc then I'm confident you're communicating with the vehicle. Why you can't access the AHC ECU isn't clear to me though. Could be the Techstream/mini VCI side or could be hardware vehicle side - as a confidence check I'd locate and confirm the SIL output from the ECU is present and confirm it goes to pin 7 of the OBD socket (which toyota calls DLC3). It could/should be the violet/white wire that's at pin 16 on the 16 pin ECU connector (there are 3 ECU connectors - a 26 pin, a 16 pin and a 12 pin).

Your summary of the system and consequences of raising the N height are correct. Essentially if you raise the N height, or add weight or both, then the hydraulics have to do more work to maintain the new, higher N height. This work translates to higher static pressures (neutral pressures) if you haven't compensated with addition mechanical lift via TB adjustment and coil spacers or stiffer AHC coils like the King KTRS -79. Higher static pressure increases the pre load pressure on the damper accumulators, compressing them and inhibiting their ability to readily absorb fluid pulses due to shock piston displacement - they basically become too hard with not enough "give" as they have too much pre load pressure and just don't function properly as a gas spring. You get essentially the same negative affects as a result of the damper accumulators loosing their nitrogen pre charge as they age. Double whammy when you have damper accumulators that have lost some nitrogen pre charge and you add weight/height or both. By increasing your height with a sensor lift you've increased your static hydraulic pressure; for instance adding 1 inch of height to the front ~ 2.2Mpa F pressure increase, not quite as bad for the rear but still significantly increases the pressure. So, at +2inch lift you might need somewhere between 10-20 turns on the TBs just to get back to the same pressure as you had pre lift. If you don't have enough threads each side on the adjuster bolts then you'll need to reindex. For the rear a 30mm spacer will lower the rear pressure about 0.5Mpa and that's usually enough to get a stock weight/height vehicle back into a zone where the rear damping static pressure is acceptable. You need to compensate for 50mm of lift so you'd probably be looking at 80+mm of spacers roughly to get a rear pressure in the 6-6.5MPa zone - not at all feasible so I'd recommend going to the KTRS-79s if you want to maintain a 2in lift.

The AHC shocks are single acting actuators ~rams~ with throttling and compensating orifices drilled through their piston. There is no gas charge in the "shock" like a conventional shock. The gas charge for each "shock" is the remote damper accumulator which is hydraulically connected to its "shock" and has an inline ECU controlled 16 step variable orifice valve assembly which allows for adaptive and user selectable damping. The front wheels are on their own leveling and damping circuit, as are the rears. The usual status is for the two front wheel "shock" hydraulic circuits to be connected, as are the rears. As a function of speed and steering wheel input the front and rear wheels may be individually hydraulically isolated for improved roll stability. The ECU damping system is a two channel system with front and rear circuits. The wheels are not independently electronically damped which would then be a four channel system.

 

[SAMTHEMAN]

If you can read DTCs, adjust user settings etc then I'm confident you're communicating with the vehicle. Why you can't access the AHC ECU isn't clear to me though. Could be the Techstream/mini VCI side or could be hardware vehicle side - as a confidence check I'd locate and confirm the SIL output from the ECU is present and confirm it goes to pin 7 of the OBD socket (which toyota calls DLC3). It could/should be the violet/white wire that's at pin 16 on the 16 pin ECU connector (there are 3 ECU connectors - a 26 pin, a 16 pin and a 12 pin).

Your summary of the system and consequences of raising the N height are correct. Essentially if you raise the N height, or add weight or both, then the hydraulics have to do more work to maintain the new, higher N height. This work translates to higher static pressures (neutral pressures) if you haven't compensated with addition mechanical lift via TB adjustment and coil spacers or stiffer AHC coils like the King KTRS -79. Higher static pressure increases the pre load pressure on the damper accumulators, compressing them and inhibiting their ability to readily absorb fluid pulses due to shock piston displacement - they basically become too hard with not enough "give" as they have too much pre load pressure and just don't function properly as a gas spring. You get essentially the same negative affects as a result of the damper accumulators loosing their nitrogen pre charge as they age. Double whammy when you have damper accumulators that have lost some nitrogen pre charge and you add weight/height or both. By increasing your height with a sensor lift you've increased your static hydraulic pressure; for instance adding 1 inch of height to the front ~ 2.2Mpa F pressure increase, not quite as bad for the rear but still significantly increases the pressure. So, at +2inch lift you might need somewhere between 10-20 turns on the TBs just to get back to the same pressure as you had pre lift. If you don't have enough threads each side on the adjuster bolts then you'll need to reindex. For the rear a 30mm spacer will lower the rear pressure about 0.5Mpa and that's usually enough to get a stock weight/height vehicle back into a zone where the rear damping static pressure is acceptable. You need to compensate for 50mm of lift so you'd probably be looking at 80+mm of spacers roughly to get a rear pressure in the 6-6.5MPa zone - not at all feasible so I'd recommend going to the KTRS-79s if you want to maintain a 2in lift.

The AHC shocks are single acting actuators ~rams~ with throttling and compensating orifices drilled through their piston. There is no gas charge in the "shock" like a conventional shock. The gas charge for each "shock" is the remote damper accumulator which is hydraulically connected to its "shock" and has an inline ECU controlled 16 step variable orifice valve assembly which allows for adaptive and user selectable damping. The front wheels are on their own leveling and damping circuit, as are the rears. The usual status is for the two front wheel "shock" hydraulic circuits to be connected, as are the rears. As a function of speed and steering wheel input the front and rear wheels may be individually hydraulically isolated for improved roll stability. The ECU damping system is a two channel system with front and rear circuits. The wheels are not independently electronically damped which would then be a four channel system.

Thanks PADDO

Its a remarkable write to study for any beginner

with regard to the AHC matter when I connect to the vehicle with the Techstream location selected to Japan there is no AHC Ecu shown in the ECU table

The AHC is only shown in North Amrerica Europe and Other locations only
But the communication is failed every time

"'as a confidence check I'd locate and confirm the SIL output from the ECU is present and confirm it goes to pin 7 of the OBD socket''

I will do the above test
What is the meaning of SIL out put??
Thanks fr the tutorial on AHC

 

[SAMTHEMAN]

Dear PADDO

Attached is the screen shot of the Cable Check I did on Techstream
Does it show any thing bad,,,

 

[PADDO]

Your pins 4,5,7 and 16 are active which is what I get and I don't have connection issues - so that's something I guess, looks normal. There's a thread from a few years back where someone was having connection issues and I posted an image of my cable check and iirc their Pin 7 was inactive. Should come up in a search.
SIL I believe stands for Software In Loop for Toyota speak. It's the single bidirectional comms cable out/in from the ECU. Similar, but not the same as, RS232 protocol.
Pin 7 of the obd connector may be referred to as K Line, for Keyword Line. I'd confirm continuity from the back of your AHC ECU (pin 16 on the 16 pin connector) to the DLC/obd connector.
Edit. Might be worth googling your particular version of Techstream for known bugs, interface issues and compatibility with your vehicle interface cable.

 

[SAMTHEMAN]

Your pins 4,5,7 and 16 are active which is what I get and I don't have connection issues - so that's something I guess, looks normal. There's a thread from a few years back where someone was having connection issues and I posted an image of my cable check and iirc their Pin 7 was inactive. Should come up in a search.
SIL I believe stands for Software In Loop for Toyota speak. It's the single bidirectional comms cable out/in from the ECU. Similar, but not the same as, RS232 protocol.
Pin 7 of the obd connector may be referred to as K Line, for Keyword Line. I'd confirm continuity from the back of your AHC ECU (pin 16 on the 16 pin connector) to the DLC/obd connector.

dear PADDO
Its late in the evening here in Sri Lanka
I am about 3.5 hrs behind you and you may have sun shining

I will be able to look at it tomorrow by 3 PM

Please give e time till tomorrow to give you the update

I appreciate your devotion to help

 

[SAMTHEMAN]

Dear PADDO,
A question about the LC 100 Shocks,,
What is the recommended interval to replace the shock absorbers?
If such a mileage is difficult to indicate what are the usual signs of shock replacement required.

mine does not have any oil leaks or physical damages visible..( to my knowledge)
Does the shock absorber play a role in softer ride in LC 100 or is it the Spheres that matter most?

 

[PabloCruise]

Dear PADDO,
A question about the LC 100 Shocks,,
What is the recommended interval to replace the shock absorbers?
If such a mileage is difficult to indicate what are the usual signs of shock replacement required.

mine does not have any oil leaks or physical damages visible..( to my knowledge)
Does the shock absorber play a role in softer ride in LC 100 or is it the Spheres that matter most?

I believe it is the nitrogen charged spheres that play the biggest role in damping. They have diaphragms in them that are somewhat permeable. Over time, the nitrogen charge can diminish...

 

[uHu]

What is the recommended interval to replace the shock absorbers?
...
Does the shock absorber play a role in softer ride in LC 100 or is it the Spheres that matter most?

The shocks on an AHC cruiser work only as hydraulic rams. As long as they don't leak, there isn't much that can go wrong.
The damping (shock absorber function) happens in the actuator, which has a 16 step damping valve.
The movement of hydraulic fluid (AHC fluid) between the shock and the sphere, through the actuator, is a prerequisite for the damping of the suspension movement.

There are a few factors that affect damping and suspension:
1: If the spheres loose their gas pressure, there will be less movement of fluid (and, eventually, less suspension travel) and therefore less damping.
2: If the AHC pressure is too high, the gas in the sphere will be more compressed, and we are back to the same result as for factor 1.
3: If the AHC pressure is too low, the ahc/spheres/hydraulics will carry too little of the vehicles weight, and will not be able to affect the suspension travel enough to dampen the movement.

Another issue, often overlooked, is that the state of the spheres does not affect ahc pressure or the Lo-N-Hi movement.

So, there is no need to change the shocks (actually rams) as long as they move freely and don't leak.
The important factors are :
1: That the pressure is correct, which is set by the state of the steel springs (coils and TB) and the set height of the suspension/vehicle.
2: That the spheres are good (They loose their pressure over time. Measured by counting graduations on the reservoir (when the pressure and height are within specs))
3: That the fluid is clean (It gets polluted over time, mainly by the material in the diaphragm of the spheres and the nitrogen gas, I believe)

 

[SAMTHEMAN]

The shocks on an AHC cruiser work only as hydraulic rams. As long as they don't leak, there isn't much that can go wrong.
The damping (shock absorber function) happens in the actuator, which has a 16 step damping valve.
The movement of hydraulic fluid (AHC fluid) between the shock and the sphere, through the actuator, is a prerequisite for the damping of the suspension movement.

There are a few factors that affect damping and suspension:
1: If the spheres loose their gas pressure, there will be less movement of fluid (and, eventually, less suspension travel) and therefore less damping.
2: If the AHC pressure is too high, the gas in the sphere will be more compressed, and we are back to the same result as for factor 1.
3: If the AHC pressure is too low, the ahc/spheres/hydraulics will carry too little of the vehicles weight, and will not be able to affect the suspension travel enough to dampen the movement.

Another issue, often overlooked, is that the state of the spheres does not affect ahc pressure or the Lo-N-Hi movement.

So, there is no need to change the shocks (actually rams) as long as they move freely and don't leak.
The important factors are :
1: That the pressure is correct, which is set by the state of the steel springs (coils and TB) and the set height of the suspension/vehicle.
2: That the spheres are good (They loose their pressure over time. Measured by counting graduations on the reservoir (when the pressure and height are within specs))
3: That the fluid is clean (It gets polluted over time, mainly by the material in the diaphragm of the spheres and the nitrogen gas, I believe)

Dear uHu
Thank you very much for the valuable comments

The first thing I want to know now is the AHC pressure

I have an Issue of connecting to the AHC ECU thru Techstream

I am following some advice given to me by PADDO

I got too busy so that I could not verify a connection wire between the DLC3 and the AHC Ecu

first three days of this week I have to attend to some work and once I get it sorted out I will check the pressures.

By the way I have ordered the manual pressure test gauge and the hose and some connectors to test in case techstream fails again

thanks again for helping me

 

[SAMTHEMAN]

Your pins 4,5,7 and 16 are active which is what I get and I don't have connection issues - so that's something I guess, looks normal. There's a thread from a few years back where someone was having connection issues and I posted an image of my cable check and iirc their Pin 7 was inactive. Should come up in a search.
SIL I believe stands for Software In Loop for Toyota speak. It's the single bidirectional comms cable out/in from the ECU. Similar, but not the same as, RS232 protocol.
Pin 7 of the obd connector may be referred to as K Line, for Keyword Line. I'd confirm continuity from the back of your AHC ECU (pin 16 on the 16 pin connector) to the DLC/obd connector.
Edit. Might be worth googling your particular version of Techstream for known bugs, interface issues and compatibility with your vehicle interface cable.

Dear PADDO,

Thanks for your advice..
I checked the connection 16 pin to Pin 7 of DLC 3,,
You're right.
For some reason the connection was not there..
I have jumped the 16th pin to DLC pin 7 via a Cable,
Then connected the Techstream and It was successful,,,

I managed to check the AHC ECU details

Please see below the BEFORE AND AFTER ADJUSTING DATA SCREEN SHOTS

Thanks for your advice's, PADDO and UhU,

I think now I m on Track with the proper tools and proper advices

I have a problem
I have set the front Height as follows
(BOTTOM OF Fender to Floor of garage, Perfectly leveled)
FRONT LEFT-845MM
FRONT RIGHT 850MM
REAR- 864 MM

THESE VALUES ARE MEASURED AFTER THE VEHICLE IS RAISED FROM LOW TO NORMAL..

When I drive the Vehicle for 10 Km I see the the values are higher than it was and teh pressures are alos high as it should be (but still with in specs)

FRONT LEFT-845MM increased to 858mm
FRONT RIGHT 850MM increased to 862mm
REAR- 864 MM increased to 874 mm

I wonder is it something wrong with the ECU or The Sensors...

When I Lower the vehicle from HIGH to NORMAL the the height is about 4 mm higher in front than raised from LOW to NORMAL

How to over come this?

How do you suggest to balance the Left and Right Front sensors?

 

[uHu]

Don't overthink the issue. Those height differences are small. The ahc system will not do any correction until the "error" is over a certain limit, it doesn't bother with a few small millimeters.
Otoh, you might have a bit looseness in the linkages, evt also combined with a high friction in the sensor shaft, but with the small differences you see, there is no reason to suspect it. Another issue that comes into play, is worn carbon traces in the sensors, which give unreliable readings, and can also give the ahc ecu an idea of you driving on very corrugated roads.
But the readings you get seem to be normal, you will get a variation of a few mm for each time you test (Not so much if you just stand still all the time). And, the difference between going from Hi to N and going from Lo to N can be much bigger than that.

For the left/right balance, you adjust the torsion bars, as described in several threads here. Althogh your L/R diff is very small.

 

[SAMTHEMAN]

Don't overthink the issue. Those height differences are small. The ahc system will not do any correction until the "error" is over a certain limit, it doesn't bother with a few small millimeters.
Otoh, you might have a bit looseness in the linkages, evt also combined with a high friction in the sensor shaft, but with the small differences you see, there is no reason to suspect it. Another issue that comes into play, is worn carbon traces in the sensors, which give unreliable readings, and can also give the ahc ecu an idea of you driving on very corrugated roads.
But the readings you get seem to be normal, you will get a variation of a few mm for each time you test (Not so much if you just stand still all the time). And, the difference between going from Hi to N and going from Lo to N can be much bigger than that.

For the left/right balance, you adjust the torsion bars, as described in several threads here. Althogh your L/R diff is very small.

Dear uHu
Thanks for the prompt reply
I will take your advice
I will not mendle with the system any more!!!

 

[RaikoJ]

Hello guys.

I have the problem with the AHC, rear suspension making noice and bounces. I did some tests and maintenance too. I change the AHC fluid and my system is giving 14 graduations from Lo to Hi. Car is holding Lo-med-Hi positions without any problem. Everything seems to be okay. I read this topic and didn´t understand, whats next...rear coil spring need to change or i need to change shocks also or what is taking those disturbing bounces away?

 

[uHu]

Start with the basics - What are your heights and neutral pressures. For the noise - Find out what is making noise....