Definitive list of AHC maintenance items

[Wilsil]

A question for those who did change the AHC coils with non-AHC coils.
Is there a difference between left and right?
I can't see any difference in the ones I have (still in the garage, I know I still have to do it)

 

[CappyKD]

Yes there is. The drivers side is a bit taller.

 

[Wilsil]

Will have a check again. Last time I couldn't see any real difference between them.

 

[CappyKD]

I know Usdm 100'S have two different part numbers.

 

[Wilsil]

Yes there is. The drivers side is a bit taller.

Had another look yesterday and measured both of them. There is a difference of 3mm........

 

[mummy3]

You can check this yourself if you order one of these: http://www.uobd2.net/wholesale/mini-vci-for-toyota-tis-techstream-v500028-single-cable-2442.html

This cable connects a laptop running Windows to your car's OBDII connector. Once you run TechSteam (Toyotas service software) you can read the pressures for the front and rear.

I ordered and used it to reset ahc. Worked ok

 

[deanfun]

Finally did some adjustment on my '07 LX. 110kms on the truck. New fluid approx 15k kms ago, new land cruiser AHC springs about a year ago. Truck is parked in a garage year round, but during winter sees -30C to -40C temperatures to +30C in the summer. I'm not sure if temperature swings play a part in AHC condition/effectiveness, but that big of a variation certainly can't help

After playing with the FL sensor, I was left with:
FL height -2.6mm
FR height -2.4mm
RR height -0.4mm

Front pressure 7.0mpa
Rear pressure 6.2mpa

Initial FL height was lower, which I'm led to believe is typical with someone always in the driver seat. I did not adjust the torsion bars. Front pressure reduced from 7.2mpa to 7.0mpa upon raising the FL height. I'm happy with the front pressure where it is, but had hoped that the rear would be in better shape with new springs. I'm going to order some 10mm trim packers for the rear springs and see where that gets me. Anyone have any suggestions on where to grab those?

 

[uHu]

.... I'm happy with the front pressure where it is, but had hoped that the rear would be in better shape with new springs. I'm going to order some 10mm trim packers for the rear springs and see where that gets me. Anyone have any suggestions on where to grab those?

Have you measured the actual heights? If the tail is too high, the pressure will be too high as well. I.e. if the rear sensor is adjusted too high, the sensor will still read ~0 mm, but the height will be higher than standard and the coil will be less compressed than it should be, and therefore take less load off the ahc.

 

[PADDO]

As uHu says, pressures and height readings from techstream must be taken in context and referenced back to the physical height of the vehicle as per the FSM if you want to dial everything in for stock height at stock weight.

 

[deanfun]

Have you measured the actual heights? If the tail is too high, the pressure will be too high as well. I.e. if the rear sensor is adjusted too high, the sensor will still read ~0 mm, but the height will be higher than standard and the coil will be less compressed than it should be, and therefore take less load off the ahc.

I measured a 1" difference F-R from fender to bottom of rim, which aligned with what I've read on here.

 

[Bryanl]

Heading to Hundreds in the Hills in one week and need some input.

Replaced the front upper control arms, removed the lower control arms to replace the ball joint which meant taking the torsion bars loose. Everything is back together and have techstream running. I haven't had the front end aligned yet and it is off with negative camber in the front left for sure. I went to fill up and did all testing in the garage which is reasonably flat, nobody inside so unladen. All height sensors all the way up and for all test accumulator pressure was around 10.2.
FR 0.6 FL -0.7 Rear -0.1
Front 5.9 Rear 7.0
After several adjustments of the torsion bars and rear height sensor.
FR 0.0 FL -0.1
Front 7.1 Rear 6.5

Looks pretty good but something is way off. The front left is an inch higher than the front right. The tension on the torsion bars is way off as well. A lot of pressure on the front left and not much on the front right. The right is noticeable looser based on the marks I did when removing. Also obvious if you look at how many threads are showing on the adjustment nuts indicating a large difference. To me the tension on the FL explains the height difference. Yet, I also wonder if it's due to the front sensors and they need to be adjusted to level the front end height? Then I need an alignment but I feel like I'm caught in a vicious circle and need input on where to start.

This thread made it sound like baseline the front cross heights being equal and then adjust the bars equally for the right pressure. Should they be checked with a driver inside? I'm 170 and doubt that is going to make that much of a difference and that the sensors would adjust.

Anyone have a suggestion on which egg to crack first? Set the tension on the bars equal and go from there, get an alignment to make sure the weight on the front end is somewhat correct and then make adjustments for the pressures and maybe another alignment? Start all over on the torsion bars and see if I can figure out how to reindex the bars in case one is off baseline when they were loose? Adjust the height sensors some to level the front ride height?
As you can see I'm lost.

 

[PADDO]

You need to get your front cross level within 10mm, so loosen up your FL TB a few turns and tighten your FR the same amount - split the difference. When you're satisfied that you're pretty close to cross level take height readings at all four corners so you can set your desired rake. Now is the time to adjust height sensors if necessary (the front sensors don't change cross level, just superimpose + or - height onto the mechanical system, so if the TBs are skewed you'll just end up higher or lower but still not level). Last thing to do is tighten or loosen both TBs (the same amount both sides to preserve your cross level you just established) to dial in your pressure for the front, rear is determined by your coils and their free length so no easy adjustment there unless you have air bags.

Chasing techstream heights and pressures while the vehicle isn't cross level and not at your desired height physically is just going to frustrate the hell out of you. I'm not sure if you've moved your sensors to up your neutral ride height, if so you'll have higher rear pressures (unless you've got bags or taller springs/spacers). I set my pressures whilst in the vehicle (190 lbs) and my weight adds about 0.2MPa. In your situation I'd work towards getting it cross level, then at the right height and lastly dial in pressures as best you can.

It'll all fall into place, just attack it sequentially.
Edit. Don't use techstream until you're ready to adjust pressures and fine tune your front height sensors to be pretty closely matched because I think it's giving you more info than you need. Just use a tape and 30mm socket to get cross level. Then use the tape to measure all four corner heights and tweak sensors to move the vehicle front/rear up or down and when you're satisfied then hook up techstream to tune pressures and balance the front height sensor readings. They work out the actual displacement and the ECU works out an average and commands an up/down signal to get the sum displacement to zero or if one sensor says +2 and the other says -2 then the sum displacement is 0. Ideally, after you have your physical height where you want it use the techstream FL and FR height numbers to incrementally get the displacement signals close, within 0.3 inch delta is fine.

 

[Bryanl]

Thank you Paddo! I didn't know the correct sequence, was already frustrated that I probably could have done it better without using techstream. I was trying to make the height cross level within .1 of 0 from techstream. But the cross level is the actual vehicle height with a tape measure. Now realize it doesn't matter if the front heights are both -2.0 as long as they are similar. And I had moved all the sensors up as high as they would go on the adjustment slots-haven't done anything with the threaded rods. So:

1. Set the front end cross level to within 10 mm by adjusting the torsion bars and using a tape measure.
2. Adjust height sensors so I have the desired rake which I think I have read is 1 inch--need to determine where those measurements are taken for all four corners if it's different than using the wheel well heights? Looks like the FSM page above has the info. if I can read it. I have larger tires and wouldn't mind it sitting up higher but not at the expense of ride quality.
3. Hook up techstream and make sure the front height sensors are close together while cranking the TB's to get the desired pressure.

I'm just concerned with getting the front (TB's) set so I can get it aligned and make it safe for the trails at HIH. I'm going to buy a new set of rear coils when I get back and see what that does for the rear pressure-after 16 years and almost 300k miles I guess they could be fatigued (sarcastic).

Thanks for pointing me in the right direction!

 

[PADDO]

Excellent, love it when a plan comes together! Couple of things: rake of .75 to 1.0 seems to work. For stock height at the FSM settings in that screen shot I posted you'll measure about 19.75 inch F and 20.5 inch R from centre of centre cap to bottom of wheel arch. If you've gone for a bit of sensor lift you'll have new numbers but try for that 1 inch rake. Don't forget that TBs really only do two things in an AHC vehicle 1. Set cross level and 2. Adjustable for neutral pressure. Your height sensors set the height. Sounds like your on top of it all now, enjoy HIH5!

 

[Bryanl]

PADDO rules. Put the torsion bars about where I thought they should be and that got the cross level close off the bat. Little more fine tuning to get them almost exact. Heights were in line with guidance so then I went to techstream and continued to tune.
FR 0.2 FL -0.3 RR -0.1
Front 6.9 Rear 6.7 Accum 10.3

Guess I could have played with the front height sensors a little more but want to get the front end aligned since it is so far out right now and if needed make some adjustments for a final alignment.
Thanks for getting this noob set straight to enjoy HIH5!

 

[looking4lc]

hi guys, noob here with few Qs. just got the readout on my LX and it seems like i need to adjust the TB on front and rear.
3 months ago, i did an alignment and the shop measured the heights from the fender lip to the ground and started cranking the TB with the gun while the car was turned off and lifted. and here is my readyng. my Qs are:
1- do i need to adjust the sensor or just crank it till meets Spec? is it one bolt for the front or two each side?
2- will it make any difference on heights?
3-what is the Specs from fender lip to the center cup?
4- how will i know if front or rear coils should be replaced? or when?

AHC is working fine and did a flush last year.
i am planning on doing this next couple of days so i appreciate it if i can get help soon !!

Thanks Again

 

[PADDO]

View attachment 1110413
hi guys, noob here with few Qs. just got the readout on my LX and it seems like i need to adjust the TB on front and rear.
3 months ago, i did an alignment and the shop measured the heights from the fender lip to the ground and started cranking the TB with the gun while the car was turned off and lifted. and here is my readyng. my Qs are:
1- do i need to adjust the sensor or just crank it till meets Spec? is it one bolt for the front or two each side?
2- will it make any difference on heights?
3-what is the Specs from fender lip to the center cup?
4- how will i know if front or rear coils should be replaced? or when?

AHC is working fine and did a flush last year.
i am planning on doing this next couple of days so i appreciate it if i can get help soon !!

Thanks Again

From the screen shot you've posted your pressures are way high and this can't be giving you the ride quality these systems are capable of. I guess the alignment shop unloaded your front without knowing what they were doing. Don't touch your sensors at this stage. Stock height specifications are approximately 19.75 inch front and 20.5 rear, measured from fender bottom to centre of centre cap. Actual measurements are much more particular and they are detailed in the screen shot I've posted several posts up. 19.75 and 20.5 inches at the fenders is good enough. Unless your front and rear heights are somewhat different to 19.75/20.5 there is no need to touch your height sensors.

So I expect you'll just need to make sure your cross level is satisfactory (by adjusting one or possibly both torsion bar bolts if you're way off level - splitting the difference) and then adjust both bolts equally to lower your front pressure. There is one 30mm bolt on each side, one full turn CW on both bolts will lower your neutral pressure approx. 0.2MPa, so you most likely have to crank on CW 6+ turns (to increase TB tension and therefore lower hydraulic pressure) both sides to get down to 6.9 or thereabouts. Initially taking fender/centre cap height measurements (engine running and vehicle settled at N) at each wheel is necessary to understand if you're cross level and you have the appropriate front to rear rake.

Height sensors control height, not torsion bars in AHC vehicles so adjusting your torsion bars doesn't change the functional height, it does change the static height whilst adjusting with the engine off but the Active part of Active Height Control will self adjust levels/height with the engine running.

You have torsion bars at the front, their tension is adjustable via the bolts. Rear coils should to be replaced when you can't get neutral pressures down to spec (when the vehicle is at stock height/weight) which is 5.6-6.7MPa, personally I think the lower the better in this range. If your coils are original they should be replaced in all likelihood.

I've previously posted up the actual FSM pages for adjusting vehicle height and neutral pressures, search my posts under something like "AHC FSM" and you'll get hits and you should find those pretty helpful.

 

[looking4lc]

Thank you very much paddo. That was very helpful.
Will start cranking later on.

 

[looking4lc]

paddo. Is there adjustment needed on the back one?

 

[looking4lc]

I cranked it to spec but the rear is 7.1 now.
What's next?