Quick question about AHC ride with extra weight (1 Viewer)

[ParaJake]

Hey guys, I have a 2006 land cruiser and I like the ride on it for the most part but I feel I may be missing out on something due to having AHC problems. Everyone says the land cruisers ride like clouds, but its not all THAT smooth to me. It rides pretty good, but only slightly better than my 2003 stock 4runner that I traded for this 100 series.
My 100 won't drop to low or lift up to high. This isn't a huge issue to me if its not causing any deficit in the ride. But, I had never ridden in a land cruiser prior to buying this one and I have never ridden in any other land cruiser so I don't have anything to compare it to.

After starting my car and driving for a few seconds, the AHC OFF light flashes constantly. I had this checked by a Toyota dealership and they said it was all of the height sensors. Does this sound right? That ALL of the sensors are bad? Or is it a fluke?

I'd love to get this thing working 100%, but I can deal with non-working AHC for now.

My main question is about riding with passengers in the 2nd row seats. When I have passengers in the second row, the ride gets very bad and I feel bad for the people in the back. It feels like the suspension is bottoming out with no more than 500 lbs in the back seat. This can't be right as I know the towing capacity is way more than that and I know that this thing is rated for more than just a measly 500lbs of human flesh bags in the back. Its actually more like 400lbs. Could this rough ride be due to a failing AHC system? It doesn't ride bad with myself and another in the front seats.

Also, does the ride stiffness control knob (next to the AHC position button) work if the AHC height sensors are bad?

I'd like to mention also that my AHC height control has never worked since I bought this about 7 months ago.

 

[IndroCruise]

I am running the active tests on each one of the systems on the active test screen. Im not sure what to do here. All that happens is a little screen pops up with a left and right arrow and the option to turn things on or off via the arrows. However they all show up as off initially. But when I switch them to on, they instantly go back to off. Is this how it's supposed to work?

To avoid being diverted by the mysteries of Techstream and for more control, I avoid Techstream for this purpose and use the specified manual method set out in the relevant attachment to Post #19, and as below:

1. With Ignition OFF, connect terminals Ts and E1 at DLC1 (this is the socket in the engine bay, usually over the RHS wheel arch with the word DIAGNOSTIC on the top cover. The terminal "map" is shown inside this cover. Instead of Special Service Tool (SST) 09843-18020 which is just a piece of bridging wire, find something simple -- I use an unbent paperclip for this test. Voltages are low here low, about 4.5 volts, and will not cause a problem -- but be careful to connect the correct terminals,
2. Turn ON the engine.
3. Push the DOWN button on the Height Select switch within 5 seconds of engine start and hold it down for 5 seconds. There will many flashing lights in the instrument cluster (because the ECU has been by-passed). Ignore these -- they will revert to normal later, after the test, when the bridge (paperclip) is removed and the AHC ON/OFF switch is pressed down for a couple of seconds,
4. Use the combined settings to move front or rear up or down (listen for the operation of the AHC Pump and its motor)
5. When finished, switch OFF engine, then remove the bridge (paperclip),
6. Re-start, push down the AHC ON/OFF for a couple of seconds to clear the test.

 

[IndroCruise]

To get started, just adjust one. I don't think it matters right now. You'll be fine-tuning them later, but let's just get the basics functioning first. Take either front sensor and move it on the slider and recheck your values. Adjust until your fronts are closer to even. Within .5" should be plenty.

Once you get that pump running, then you can fine tune all the heights.

I agree with @suprarx7nut .

In my case, I try to do these adjustments by having the screen where I can see it next to where I am working and can watch the readings in real time as I play with the Sensor adjusters (may need a USB extension lead for Techstream on a laptop, I use an ELMscan327 device and Bluetooth to make it easy).

Engine is OFF. Ignition and Techstream are ON. Wheels are on the ground and straight ahead -- which at the front means reaching around the wheel to get to the Sensors -- and is why I mention earlier to focus on the sliding adjusters because it is very convoluted and fiddly to deal with the heim bolts in this position. Adjusting the Rear Sensor means being under the vehicle.

It is important that the engine is OFF -- you do not want the AHC system waking up, trying to make corrections, and moving the vehicle up or down.

Mistakes can be made, so have jackstands in place under the chassis rails (but not taking weight), so that it is PHYSICALLY IMPOSSIBLE for the vehicle body to drop onto the human body.

Whatever, the aim is to get ALL Sensor readings as close as possible to zero, FSM suggests zero +/- 0.2 inch, but don't sweat it too much, just try to get rid of the very large differences from zero at each Sensor. The purpose at this stage is to eliminate so-called 'fail-safe' mode as a possible cause of AHC non-operation. Fine tuning can come later, when AHC system actually is working.

@suprarx7nut or other IH8MUD members may have a more elegant method of doing these adjustments ....

 

[ParaJake]

I have adjusted each to their outer limits. I mean BARELY any threaded rod left in the couplings at each end. Without me sitting in the vehicle, the FL -0.7 and FR -.06.

When I'm in the vehicle FL -1.0 and FR -0.5.

RR -0.9

Still can't hear the AHC motor turning on

Still can't run any active tests.

I'm thinking
1.) The adjustment rods on the height sensors are not safe where they're at being at the very ends of the threaded adjustment rod and
2.) This isn't the height control sensors.

I'd like to check the voltages of certain things to make sure they have good connections and that everything is working properly. The battery is relatively new at less than a year old.

@IndroCruise I am unsure of what "sliders" you are talking about. The only adjustable piece I can see on the front sensors are the heim joints. They aren't easy to get to while the wheels are straight. Luckily I have a lift I have the vehicle on. I do keep bringing it down to check the actual measurements of the sensors with vehicle weight.

 

[IndroCruise]

I have adjusted each to their outer limits. I mean BARELY any threaded rod left in the couplings at each end. Without me sitting in the vehicle, the FL -0.7 and FR -.06.

When I'm in the vehicle FL -1.0 and FR -0.5.

RR -0.9

Still can't hear the AHC motor turning on

Still can't run any active tests.

I'm thinking
1.) The adjustment rods on the height sensors are not safe where they're at being at the very ends of the threaded adjustment rod and
2.) This isn't the height control sensors.

I'd like to check the voltages of certain things to make sure they have good connections and that everything is working properly. The battery is relatively new at less than a year old.

@IndroCruise I am unsure of what "sliders" you are talking about. The only adjustable piece I can see on the front sensors are the heim joints. They aren't easy to get to while the wheels are straight. Luckily I have a lift I have the vehicle on. I do keep bringing it down to check the actual measurements of the sensors with vehicle weight.

Sorry to be unclear -- the Front Sensors also can be adjusted by loosening and sliding the bolt up or down the slot to which it is attached.

 

[ParaJake]

@IndroCruise

......I can't believe I didn't notice those before. Thanks!

 

[IndroCruise]

@IndroCruise

......I can't believe I didn't notice those before. Thanks!

Extract from FSM added as a late edit a few minutes ago which also may help ....

 

[ParaJake]

I've adjusted them as close as I can get them. Both of the sliders and heim joints maxed is giving me the closest numbers. Something isn't adding up with the way these adjustments are correlating to the numbers. Its like one side is reading backwards. I'll have to mess around with this some more tomorrow if I get a chance. It's getting fairly late here.

I appreciate all the help I've gotten today from everyone. You guys' knowledge about this is unending and unfathomable to my tiny pea brain.

 

[suprarx7nut]

I've adjusted them as close as I can get them. Both of the sliders and heim joints maxed is giving me the closest numbers. Something isn't adding up with the way these adjustments are correlating to the numbers. Its like one side is reading backwards. I'll have to mess around with this some more tomorrow if I get a chance. It's getting fairly late here.

I appreciate all the help I've gotten today from everyone. You guys' knowledge about this is unending and unfathomable to my tiny pea brain.

My advice is to not get too hung up on the height sensors if you have them reading within .5" of each other. If the front sensors agree more or less and the pump still doesn't run, I think you have another problem stopping you from success here.

 

[IndroCruise]

I'd like to check the voltages of certain things to make sure they have good connections and that everything is working properly. The battery is relatively new at less than a year old.

Mmmm -- seems like this situation may need a new day, a fresh start and new ideas!!

Taking stock from the descriptions in your posts and if I have understood them correctly, some of the details include:

1. Low IG power source voltage (around 12.3 volts) -- not yet explained,
2. Extremely low +B power source voltage (1.5 to 3.0 volts) -- not yet explained,
3. Cross-level is good,
4. Tape-measured hub-to-fender 'ride heights' are a bit low at front and rear -- but are unlikely to be a problem,
5. All three Height Control Sensors are new replacements -- no reason given to doubt reliability,
6. All four 'globes' may be past their best -- not yet replaced,
7. Ride quality is not good, worse with rear passengers,
8. Readings from new Height Control Sensors initially showed large differences -- re-adjusted, now 'reasonable' (?),
9. No response to "UP" or "DOWN" height control switch on centre console -- AHC dash light blinks except if "N" is selected,
10. No response to "COMFORT", "NORMAL", "SPORT1", "SPORT2" switch on centre console,
11. Vehicle does not respond to "ACTIVE TEST" by Techstream,
12. Vehicle does not respond to "ACTIVE TEST" by FSM-specified manual method,
13. Existing DTC (or DTC's) have been cleared and have not returned -- no DTC's now showing on Techstream,
14. 'Fail safe' mode due to Sensor conflicts has been considered -- problems appear to be deeper than Sensor issues alone,
15. AHC Fluid may be old -- age unknown,
16. AHC Pump has not been heard working -- inaudible during attempted tests and when vehicle is driven,
17. Vehicle is relatively new to current Owner -- previous history unknown,
18. Owner believes AHC has not worked during his ownership of the vehicle -- approximately 7 months,

With the above observations in mind, may I suggest that it is worth going back yet again to the FSM "Diagnostics" section:
https://lc100e.github.io/manual/
At this link, use the Index on the left hand side of the opening page and follow these tabs:
Repair Manual > DIAGNOSTICS > ACTIVE HEIGHT CONTROL & SKYHOOK TEMS

Before getting into all the detail, at the start this section of the FSM outlines a diagnostic process and among other things explains situations in which DTC's may not be recorded even when faults or 'difficulties' exist.

The upshot is that the presence of a DTC may help to identify and fix a problem (and usually does).

However, the reverse is not true.

The absence of a DTC does not provide any guarantee that there is no problem.

FSM Page DI-221, headed "Problems Symptoms Table" is very explicit: "If a normal code is displayed during the DTC check but the problem still occurs, check the circuit for each problem symptom in the order given in the table and proceed to the relevant troubleshooting page".

The "Problems Symptoms Table" is attached and gives the FSM recommended starting point and sequence of investigation when symptoms occur and when there is no DTC to help interpretations.

Before getting too complicated, it is worth doing two preliminary things:

• understand the strange IG and +B voltage results -- may need a question to a somebody who is good at auto electrics,
• checking the actual condition of the console switch even though there are no DTC indicators -- test details are found in FSM Diagnostics at C1786, C1787, C1788 -- also see pics at Suspension problem even after replacing almost everything - https://forum.ih8mud.com/threads/suspension-problem-even-after-replacing-almost-everything.812905/page-2#post-9444084 -- can be subject to spills of water, coffee, etc.

After that, I think I would test the AHC Pump as suggested way back by @ramangain -- and maybe that idea should have been supported at the beginning of this saga! This can be done when the pump should be operating by listening (the sound is distinctive above the engine noise, or, put an ear on screwdriver resting on the motor), or by putting a hand on the pump.

Or cut to the chase by pulling the electrical connector at the pump and using leads to apply 12 volt battery voltage directly to the pump motor terminals. Details are shown at C1762 in the FSM Diagnostics -- obviously be careful not to touch the leads together while getting them on the pins at the Pump!

If the Pump does not work, then it is necessary to figure out the cause:

• blockage in the AHC Pump itself, noting that the age and condition of the AHC Fluid is unknown -- there are some posts on IH8MUD about such blockages, for example, pics at -- replacing AHC globes/accumulators - https://forum.ih8mud.com/threads/replacing-ahc-globes-accumulators.716383/page-18#post-13953612, or,

• failure of the pump motor itself -- unusual, but has been reported previously.

If the AHC Pump does work -- then life becomes "interesting"! Why does the pump work when directly powered, bypassing the ECU, but does not work when it is under the control of the ECU as part of the AHC/TEMS system??

Possibilities include a fuse or relay failure preventing power getting to the Pump -- several of these problems have been reported previously on IH8MUD. One example is the well-hidden AHC IG fuse which resides behind the left-hand cover in the left-hand footwell -- 2003 Amazon ahc no power to relay - https://forum.ih8mud.com/threads/2003-amazon-ahc-no-power-to-relay.1252055/#post-13842896.

If chasing this down these kinds of problems, suggest a methodical approach, looking at the possibilities one by one.

Among these there are a range of 8 different problems which give rise to at least 8 slight different forms of 'fail safe' mode marked with double asterisk **, and which may cause the AHC Pump not to operate. These 'symptoms' may occur with or without recorded DTC's. The possibilities are set out on the trouble-shooting pages in the following list, all to found in the FSM Diagnostics section.

C1711 to C1713 – **Height Control Sensor Circuit (already discussed and investigated)

C1718 -- **Fluid pressure sensor

C1721 to C1723 -- **Damping Force Control Actuator Circuit

C1731 – C1736 -- **Control Valve Solenoid & Accumulator Valve Solenoid Circuit

C1741 -- **AHC Motor Relay Circuit

C1743 -- **Main Relay Circuit

C1751 -- **AHC Pump & Motor Circuit

C1762 -- **Fluid Pressure Abnormality (Pump & Motor does not supply fluid)

C1763 – C1764 – **Fluid Pressure Abnormality (Valve does not open)

C1786 -- Height Select Switch

C1787 – Damping Mode Select Switch

C1788 – Height Control Switch Circuit

May I suggest that it is worth skimming each of these pages in the FSM Diagnostics section, looking at the 'fail safe' description. Consider which of these possibilities best matches your 'symptoms', then consider the FSM-suggested tests or other IH8MUD-suggested ideas which might be most relevant.

This '"menu" definitely will give you a few voltages, resistances, continuity and other things to check so as to work out what is working properly and what is not working as it should.

A new day will soon start in Ohio! Good luck!

 

[Rebus Knebus]

Before getting too complicated, it is worth doing two preliminary things:

• understand the strange IG and +B voltage results -- may need a question to a somebody who is good at auto electrics,

This.

Start with what Techstream is reporting as obviously wrong before chasing down a bunch of “possibly” kinds of things. Check out the EWD in the online FSM. The “+B” to the ECU comes from the AHC Main Relay (which is different from the AHC relay which powers the pump). Start by checking voltages and operation of this relay.

 

[uHu]

I've adjusted them as close as I can get them. Both of the sliders and heim joints maxed is giving me the closest numbers. Something isn't adding up with the way these adjustments are correlating to the numbers. Its like one side is reading backwards. ...

You might have two left side sensors, or two rights. It's been a few years since last time I had to touch this, but iirc, the left and right sensors are opposite of each other, and the rear is equal to one of them.

 

[ParaJake]

You might have two left side sensors, or two rights. It's been a few years since last time I had to touch this, but iirc, the left and right sensors are opposite of each other, and the rear is equal to one of them.

I thought this may be the case. However, one has L and one has R stamped into the side. And if they were the same, it would be pretty hard to physically attach them their respective mounting locations

 

[uHu]

Yes, the brackets are different, but you can change the sensor without changing the bracket. The difference might be only in the lid of the sensor, where the carbon traces are - if you take the cover off, one should be a mirror image of the other. Warning: I haven't checked to see if there are other differences as well.

 

[ParaJake]

Unless something got messed up at the factory, they should be the correct ones. I never opened them up, I just put them on.

 

[uHu]

Here's one left and one right. Don't know which is which:

 

[ramangain]

Can you post a fresh screen shot of those AHC parameters in Techstream while the vehicle is running and sitting in Park?

 

[ParaJake]

Thanks @uHu

Now I just did some adjusting and something Is definitely not right. I'm adjusting the sliders, not the heim bolts, now.

When I adjust the FL higher towards the top of the slider groove, the sensor value in TechStream DECREASES. I have it adjusted to the top now, and it's reading -1.0. At the bottom it was reading -0.7

When I adjust the FR higher towards the top of the slider groove, the sensor value in TechStream INCREASES. I have it adjusted to the top now and it's reading -0.0. At the bottom it was reading -0.3.

Which one is correct? It's possible that there is a duplicate sensor in the incorrect housing.

 

[ParaJake]

@ramangain

Taken just now. Vehicle running, in park. Myself outside of the vehicle. FL slider all the way down towards the floor. FR slider all the way to the sky.

 

[ramangain]

TY. With that small delta between height sensors, still no AHC pump action when pressing the UP switch?

Remember, all doors, tailgate, etc must be closed for the AHC pump to start. At least on my rig.

 

[ParaJake]

TY. With that small delta between height sensors, still no AHC pump action when pressing the UP switch?

Remember, all doors, tailgate, etc must be closed for the AHC pump to start. At least on my rig.

I can't hear anything turning on, whirring, or otherwise when pushing the switch. All doors closed including tailgate.