The ABCs of AHC - How to Measure, Flush, and Adjust all in one place (7 Viewers)

[IndroCruise]

Something is not working with your TechStream or with the AHC. Which Trouble Code do you have? (Your TechStrem page says there is one)
Does it move from Lo to N? And still no movement in the pressure readings?
Do the height sensor numbers change when you go from Lo to N?
What about actual heights - are they at spec?

That the damping step numbers are fixed on 8 could indicate that you are in "limp mode". You could check the pressure sensor on the pump. Do you have the FSM?

Also, if the TBs have not been adjusted for a year or more, you can safely tighten them a few turns, to make it lighter for the ahc to lift.

I have replied to your PM and requested very similar information to the questions raised by @uHu, so that help can be provided.

@uHu also has noticed in the Techstream readout attached to your post #108 that “Front Wheel Step” and “Rear Wheel Step” are both showing “Step 8”. This is mid-way in the damping range of 16 Steps provided by the Damping Force Actuators, one for each wheel, to which the ‘globes’ are attached. (1 = very soft damping; 16 = very hard damping).

A simple test you can run is to connect Techstream and ask someone else to drive the car while you look at the laptop screen. If the TEMS part of the AHC/TEMS system is behaving normally, then you will see these “Step” readings change in (almost) real time in response to road conditions. It is worthwhile to observe these “Step” readings at each of the four positions on the “Comfort” switch. Separately, you also could observe whether “Damping Force Switch 1” and “Damping Force Switch 2” change as they should when you move the Comfort switch to different positions.

The purpose of the above simple tests are to indicate whether the AHC/TEMS system is working or not.

If the AHC/TEMS system remains at “Step 8” during this test, then that would confirm that the system is stuck in one of its “fail-safe modes” as suspected by @uHu. If stuck at “Step 8” in this “fail-safe mode”, then there will be no variable damping and the ride quality will be harsh, especially at low speeds.

If the vehicle is in a “fail-safe mode”, then it remains to diagnose what has caused this situation.

Responses to the questions raised by @uHu and in my PM will help IH8MUD Members help you to identify the cause with less guesswork.

 

[Kat Man]

Don't forget to baseline your 100. If you decide to keep your AHC you need to watch your weight/AHC pressures to keep the system working properly.

Thanks I love these resources and all the knowledge.

 

[AZ470]

Hoping someone can help with my poor understanding of the system. I've done a bit a reading on this thread and others. I've got front heights about equal at 19.5 but the rear is sitting at 20.25 left and 20.75 right. My thought is that I need to adjust the torsion bars to deal with the "lean" in the rear even though this might drive the front measurement out of wack, I should be able to fix those with a sensor height adjustment at each front wheel? Since there is only one sensor to adjust the rear height and each front wheel has it's own sensor that's the only way i can see to make everything level. I'm sure i have a poor understanding of how this works, but I can't figure out how to level the truck otherwise. I've measured graduations and pressures and plan to flush the fluid prior to doing the cross leveling in accordance with the ABC's but I don't think that should affect the rear heights. I recently installed King prings and verified they are seated correctly. Can anyone back me up with the logic?

 

[ramangain]

What does TS say about your front sensor heights?

 

[AZ470]

What does TS say about your front sensor heights?

FR 0.1 FL -0.2 was the average. Rear measurement was -0.1 across four different samples.

 

[suprarx7nut]

Hoping someone can help with my poor understanding of the system. I've done a bit a reading on this thread and others. I've got front heights about equal at 19.5 but the rear is sitting at 20.25 left and 20.75 right. My thought is that I need to adjust the torsion bars to deal with the "lean" in the rear even though this might drive the front measurement out of wack, I should be able to fix those with a sensor height adjustment at each front wheel? Since there is only one sensor to adjust the rear height and each front wheel has it's own sensor that's the only way i can see to make everything level. I'm sure i have a poor understanding of how this works, but I can't figure out how to level the truck otherwise. I've measured graduations and pressures and plan to flush the fluid prior to doing the cross leveling in accordance with the ABC's but I don't think that should affect the rear heights. I recently installed King prings and verified they are seated correctly. Can anyone back me up with the logic?

The system only raises and lowers front and rear. It cannot move left or right sides up or down. Moving sensors does nothing for lean.

To correct lean, all you can do is move the torsion bars or add spacers in the rear. I would be ok with a .5" difference in the rear. I've played around with my adjustments a few times and it's just hard to get the rear to settle even.

 

[ramangain]

The system only raises and lowers front and rear. It cannot move left or right sides up or down. Moving sensors does nothing for lean.

To correct lean, all you can do is move the torsion bars or add spacers in the rear. I would be ok with a .5" difference in the rear. I've played around with my adjustments a few times and it's just hard to get the rear to settle even.

Agreed. Let us know if the delta changes when comparing a full and empty gas tank

 

[rekab6969]

Hi Al,

Blew a AHC pipe that runs front to back near side UK, haven't looked at it yet.

Can you point me to a exposed parts list for part numbers please?

Thanks in advance,

db.

 

[suprarx7nut]

Hi Al,

Blew a AHC pipe that runs front to back near side UK, haven't looked at it yet.

Can you point me to a exposed parts list for part numbers please?

Thanks in advance,

db.

I think there are a couple different part sets pending your exact model, so this is likely wrong. However, if you happen to have a RHD VX from 2001 with the 2UZ and an automatic, here's a page of numbers that might be helpful, haha. SIgn up for Toyo DIY and go explore yourself.

 

[rekab6969]

Ahh.. yes should mention that I have 2005 4.2 100 series Amazon. Many thanks fir the info. db

 

[suprarx7nut]

Ahh.. yes should mention that I have 2005 4.2 100 series Amazon. Many thanks fir the info. db

Guess number 2, not sure what Amazon means in the context of the codes on ToyoDIY, but here's another page.

 

[AZ470]

Agreed. Let us know if the delta changes when comparing a full and empty gas tank

Thanks all for the help and advice. I’ll see what things look like after a flush and dialing the pressures in

 

[LXKevin]

Ahh.. yes should mention that I have 2005 4.2 100 series Amazon. Many thanks fir the info. db

Ahh.. yes should mention that I have 2005 4.2 100 series Amazon. Many thanks fir the info. db

plug your vin number in on partsouq.com then search. You will find useful diagrams of each system there with part numbers and available parts.

 

[rekab6969]

I did do so and a quick search but couldn’t find the pipes. Thanks.

 

[IndroCruise]

I did do so and a quick search but couldn’t find the pipes. Thanks.

Finding the right search term at some on-line websites can be tricky. Local marketing names such as “Amazon” in your case or “Sahara” in my case usually are not helpful.

Here is how it goes with partsouq.com (based in Dubai, UAE):

Insert VIN, takes you to the relevant catalogue for your vehicle.

Then select “SEARCH” part way down the page.

Then insert search term “Height”, (takes you to group 4805 and some other parts groups).

In my case, this also then identifies my model, HDJ100R-GNAEZQ.

(“Q” means Australia, so your model designation will be slightly different and should be brought up by your VIN – in your case possibly HDJ100R-GNMEZW if manual transmission or HDJ100R-GNAEZW if auto transmission as indicated in the reply by @suprarx7nut with the toyoDIY.com list – the actual detail also should be on the manufacturer’s plate somewhere on your vehicle, usually the “B” pillar between the front and rear doors, sometimes in the engine bay. The attached "code-breaker" also may help.)

A list of relevant “tubes” and “hoses” (rather than "pipes") relevant to the vehicle then can be viewed, in my case for model HDJ100R-GNAEZQ . It is not clear whether the list is complete and if in doubt it may be best to phone partsouq and ask them.

Some parts are in stock and can be purchased, some are not in stock and are unavailable from partsouq. If unavailable, then consider megazip.com and/or amayama.com – see further hints below this list of part numbers.

Part Number Description

4898160010 TUBE, HEIGHT CONTROL, NO.1

4898260011 TUBE, HEIGHT CONTROL, NO.2

4898260012 TUBE, HEIGHT CONTROL, NO.4

4898560011 TUBE, HEIGHT CONTROL, NO.5

4899460012 TUBE, HEIGHT CONTROL, REAR NO.1

4898660011 TUBE, HEIGHT CONTROL, NO.6

4899560012 TUBE, HEIGHT CONTROL, REAR NO.2

4916360011 HOSE, SUSPENSION CONTROL PRESSURE, NO.3

4916260011 HOSE, SUSPENSION CONTROL PRESSURE, NO.2

4916460011 HOSE, SUSPENSION CONTROL PRESSURE, NO.4

4916160011 HOSE, SUSPENSION CONTROL PRESSURE, NO.1


To check stock availability at megazip.com (based in Singapore but with warehouses around the world), open their website at the Toyota page and insert the required Part No. (don’t worry about VIN at this stage).

If in stock at Megazip, the details will appear, sometimes with a picture.

Then check “Compatibility” by selecting [LANDCRUISER], then Body/Chassis [HDJ100], then check that your model designation appears in the compatibility list, in my case HDJ100R-GNAEZQ but in your case it will be something different.

If searching further for available stock, the above steps can be repeated at amayama.com, based in Japan.

Finally, your local Toyota dealer should be able to identify and supply part numbers relevant to your VIN – whether or not you buy from the dealer – and that provides the information needed to check and compare pricing elsewhere.

 

[rekab6969]

WOW!! That's just fantastic, thank you very much for taking the time to compile this info..

 

[1gr8FoSemty]

So I followed Yoda MD's cheat sheet for AHC and I went from front pressures of 7.8 to 6.8 turning the torsion bars the exact number that he recommended. However, as expected, the rear did not change much. It went from 7.3 to 7.1. I figured that if I got 30 mm spacers, all I would get would be the best of 6.6. Is that good enough to see a change or should I go ahead and buy Factory new lx470 rear springs? They are $200 new on eBay. I do not have a rear bumper or anything heavy, so probably do not need King Springs.

 

[tjb]

So I followed Yoda MD's cheat sheet for AHC and I went from front pressures of 7.8 to 6.8 turning the torsion bars the exact number that he recommended. However, as expected, the rear did not change much. It went from 7.3 to 7.1. I figured that if I got 30 mm spacers, all I would get would be the best of 6.6. Is that good enough to see a change or should I go ahead and buy Factory new lx470 rear springs? They are $200 new on eBay. I do not have a rear bumper or anything heavy, so probably do not need King Springs.

I bought new springs and saw virtually no change in pressure. Not sure why. Spacers are next.

I’ve got a sleeping platform where the removable rear seats are, otherwise stock.

 

[LXKevin]

Did you unplug your temp sensor at the pump before measuring the rear pressure?

 

[LXKevin]