Definitive list of AHC maintenance items (5 Viewers)
- Thread starter yuji
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Do you have a link to the cable you purchased? No problems just hooking it into windows?
I rechecked pressures when the truck was NOT loaded with any gear and had 1/4 tank of gas. I was showing 6.5 front and 5.6 rear. I don't think I'll be adding spacers. Fully geared up I was 6.8 front and 7.4 rear. I don't know that I would want the ride anymore stiff when unloaded.
ramangain
Clarksonian disciple
That's what she said.
Hello all
The tail of my AHC system continues, I figured it was time for an update.
In general the ride quality has improved dramatically once new globes were installed in the front, cross level etc completed, heights measured hub center to fender as per ih8 standards etc, (springs are all a bit lower than they should be) all the usual stuff, including Techstream to measure pressures (with temp sender disconnected) and they are within factory specs, so no real cause for my issues as such.
The one single largest improvement in overall ride quality other than front globe replacement was to remove the height sensors and take the covers off and clean the carbon tracks with a soft cloth and a generic electrical contact cleaner.
I have checked all input to the AHC computer and looked at the outputs while driving the vehicle (myself as passenger with the laptop) TEMS switch changes the ride from relatively soft to relatively stiff, height control works Lo-N-Hi and reverse with no issues, the damping force output fluctuates from engine off default value of 8 to engine on and normal driving between 1 and 4 etc so AHC computer is reading inputs correctly and outputting correctly. If not then the default value of 8 would be showing on the data list in Techstream. So all seems to be present and correct.
My front bars are 5/10 mm low and my rear springs are 5/8mm low so i am well aware that my springs need replacing etc
However my persistent issue remains that being that my ride fluctuates from smooth as silk to sports car hard, like the computer defaults to "8" and then back to smooth as silk again outputting a damping force between 1 and 4 again.
I did adjust my height control sensors on the weekend and they we
FL - 1.2mm +
FR - 1.2mm +
RR - 2.4mm +
checking Techstream this evening they were way out, even with the car sitting pretty much in exactly the same spot as the previous readings above.
FL - 1.2mm +
FR - 5.0mm +
RR - 14.5mm +
The RR measurement i can account for, the 2.4mm + reading was with a full tanks, so with now a 1/2 load in the tanks my rear springs have lifted, no other load. Should the AHC system account for the reduced load and bring the rear down to 2.44mm + or am i barking up the wrong tree?
However the rather large difference in the FL and FR measurements i can not account for, in any way. Are these measurements far enough out for the AHC computer to default into "8" at times and then when things come back in spec the computer returns to normal damping control? Thus giving me the poor ride from time to time?
Any input greatly appreciated
TED the LX 470
The tail of my AHC system continues, I figured it was time for an update.
In general the ride quality has improved dramatically once new globes were installed in the front, cross level etc completed, heights measured hub center to fender as per ih8 standards etc, (springs are all a bit lower than they should be) all the usual stuff, including Techstream to measure pressures (with temp sender disconnected) and they are within factory specs, so no real cause for my issues as such.
The one single largest improvement in overall ride quality other than front globe replacement was to remove the height sensors and take the covers off and clean the carbon tracks with a soft cloth and a generic electrical contact cleaner.
I have checked all input to the AHC computer and looked at the outputs while driving the vehicle (myself as passenger with the laptop) TEMS switch changes the ride from relatively soft to relatively stiff, height control works Lo-N-Hi and reverse with no issues, the damping force output fluctuates from engine off default value of 8 to engine on and normal driving between 1 and 4 etc so AHC computer is reading inputs correctly and outputting correctly. If not then the default value of 8 would be showing on the data list in Techstream. So all seems to be present and correct.
My front bars are 5/10 mm low and my rear springs are 5/8mm low so i am well aware that my springs need replacing etc
However my persistent issue remains that being that my ride fluctuates from smooth as silk to sports car hard, like the computer defaults to "8" and then back to smooth as silk again outputting a damping force between 1 and 4 again.
I did adjust my height control sensors on the weekend and they we
FL - 1.2mm +
FR - 1.2mm +
RR - 2.4mm +
checking Techstream this evening they were way out, even with the car sitting pretty much in exactly the same spot as the previous readings above.
FL - 1.2mm +
FR - 5.0mm +
RR - 14.5mm +
The RR measurement i can account for, the 2.4mm + reading was with a full tanks, so with now a 1/2 load in the tanks my rear springs have lifted, no other load. Should the AHC system account for the reduced load and bring the rear down to 2.44mm + or am i barking up the wrong tree?
However the rather large difference in the FL and FR measurements i can not account for, in any way. Are these measurements far enough out for the AHC computer to default into "8" at times and then when things come back in spec the computer returns to normal damping control? Thus giving me the poor ride from time to time?
Any input greatly appreciated
TED the LX 470
A few questions:
1. How old are the rear globes? How many gradations do you get now H to L?
2. When techstream showed 14.5mm high, was the rear actually that high as measured from wheel center to fender? The system should self-regulate back to 0.
3. Springs have nothing to do with vehicle height with AHC. The sensors control height. Your comment about springs being low is confusing.
4. There is a setting in Techstream that can offset the sensor measurements. It's bottom right in the data screen. Are your values all 0.00?
If the rear globes are new, it sounds like you might have a sensor input that's drastically changing the damping control. Speed, steering, road condition(I actually don't know how that's measured), etc...
Sorry for the slow reply. I got this cable:
Mini VCI Diagnostic Tool Cable Scanner for Toyota Lexus TIS Techstream V10 30 2 | eBay
<li> Product Features</li> <li> <ul> <li>Support all versions of OEM Toyota TIS Techstream softwares including the Latest v10.30.029.</li> <li>High reliability of products using SMD chip, and certified by CE and FCC.</li> <li>Works with all Toyota lexus scion cars worldwide from 1996...
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It came with a CD loaded with TS; install went smoothly. I'm running VMware Fusion on a Macbook Pro/OSX platform. I had an existing install of Windows 10, but the cable doesn't play nice with a 64 bit OS; I installed a 32 bit Windows 7 image and it seems to work fine. I still haven't actually jacked into the car yet, so I can't say what access I have with this version.
G’day @TED the LX470,
It is late in my part of the world and the situation described needs more thought with a clearer head. Meanwhile, here are some preliminaries. While I was writing, @suprarx7nut also has offered helpful ideas.
Regardless of load (but within the limits of the AHC system), a vehicle with a healthy AHC/TEMS system should always self-adjust to the same front and rear heights – those heights being the position at which the Height Control Sensors reach zero (or are close to zero) when the console height control is set to “N”. This is the purpose of the AHC part of the system and the way it is designed. This has nought to do with spring condition nor variation in fuel load – the AHC system is meant to compensate for those effects and maintain heights. Those spring and fuel variations should result in AHC pressure variations, not height variations.
The FSM mentions a tolerance of +/- 5 millimetres at the Height Control Sensor readings but most numbers seen on IH8MUD seem to be in a much tighter range of around 2 to 3 millimetres.
Your first set of Height Sensor Control numbers after sensor adjustment look healthy enough on their face – but there is more to think about:
FL - 1.2mm +
FR - 1.2mm +
RR - 2.4mm +
Presumably (but you need to confirm) that the above readings were done after N > LO > N movement, such as when doing AHC pressure readings?
As you have recognised, the second set of numbers after some driving around tell you that that something else is happening:
FL - 1.2mm +
FR - 5.0mm +
RR - 14.5mm +
The corresponding hub-to-fender distances physically measured by tape at all wheels, corresponding to both above sets of readings, is an important part of the information needed for diagnosis. Are they the same or different? Have the corners of the vehicle physically risen in the second set of measurements, and if so by how much? This is important because increased heights inevitably means increased AHC pressures – and these may no longer be what you thought they were when measured in a N > LO > N test -- so the cause is important.
This may be as simple as the vehicle and all its joints and bushes settling into their preferred but perhaps somewhat worn positions after some driving -- and if so, the height adjustments need be repeated and until the suspension is ‘tuned’.
There are a number of other possibilities.
One starting point is to be quite sure that the vehicle has been ‘cross-levelled’ at the front with engine “OFF” per FSM on a level surface before doing anything else – and making any necessary adjustments with the Torsion Bar adjusters and not the Height Control Sensor adjusters . The actual measurements are unimportant at this stage – equalisation is important to equalise torsion bar load and avoid building in a side-to-side lean which may confuse the sensors. The obvious assumption is that the torsion bars (and rear springs) are in near-enough equal condition albeit somewhat worn – meaning that their respective spring rates are the same or similar side-to-side even if somewhat reduced due to age and wear. As you know, on a AHC/TEMS vehicle, the heights (better expressed as hub-to-fender distances) are only adjusted by moving the Height Control Sensor adjusters. The IH8MUD standard is 19.75 inches or 500 millimetres at the front and 20.50 inches or 520 millimetres at the rear -- much easier to manage than the FSM prescription. An owner may choose different heights – the point is that whatever height is chosen will become the neutral point at which the vehicle settles at the “N” console setting. Different heights will have a corresponding effect on AHC pressures.
Next, suspicion would fall on the measured electrical condition of the Height Control Sensors – done per FSM or by measuring resistances throughout the range of movement in a method described in another thread by @uHu. For example -- See this post and later ones in the same thread. One also would want to be confident of the connector condition and harness condition (continuity and resistance) between the sensors and the AHC/TEMS Electronic Control Unit (ECU), so as to be sure that the ECU is receiving correct signals (voltages) from the sensors.
The differences in the second set of sensor readings compared to the first set, and especially the large difference between the rear sensor reading and the others are grounds for considerable suspicion – and are likely to cause the AHC/TEMS system to enter ‘fail safe mode’ with the symptoms you describe. Your observation that this happens erratically and inconsistently may correspond to a dodgy sensor or a dodgy connection or damaged wiring which sometimes connects and performs properly and sometimes does not.
When confident of all of the foregoing, one might start to wonder about the correct operation of the Control Valve Assembly – an initial impression can be gained by watching the valves operate in real time on Techstream -- and maybe even consider the condition of the AHC pump (and partially blocked tiny filters inside it) which may not be delivering enough pressure and volume to raise the vehicle consistently.
However, my recommendation would be to proceed methodically rather than jump to conclusions. The “Problem Symptoms Table” in the AHC Diagnostics section of the FSM and the experience of others at IH8MUD provide guidance on the sequence to follow. Sensors and connections come next after 'globe' condition.
See more at https://lc100e.github.io/manual/ : Repair Manual > DIAGNOSTICS > ACTIVE HEIGHT CONTROL SUSPENSION & SKYHOOK TEMS > PROBLEMS SYMPTOMS TABLE > C1711/11 to C1713/13 - Height Control Sensor Circuit
Hopefully this provides a few thought starters …..
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I suggest you follow the YotaMD Cheat Sheet. If you did pull air into the system, it's a good time to flush with new fluid which is never a bad thing.
Shocks can weep with AHC if your neutral pressures are too high. Think of it as the shock crying because you're asking it to work too hard.
The shock can have seal failures and legitimately need replacement, but start by ensuring neutral pressures are correct.
If you do need replacement, they're $200-220 each. Not bad.
View attachment 2515516
Wow... thank you for this!
Your units are set to mm. Most folks have inches as the unit. .5 inches is about 12.5mm.
Does that help address you question?
Thanks @suprarx7nut. All of my height sensor readings are low. I would expect them to be at/near zero. Then there are “height adjust“ readings and sensor readings “after adjust”. I don’t think I have seen this before. What does this mean? Do I have something set incorrectly That needs to be fixed?
The adjust numbers are an electronic alternative to physically moving height sensors. They are entered in during a utility in Techstream. If the vehicle is otherwise working well, I wouldn't sweat it.
OK. Thanks @suprarx7nut ! So I use the adjusted numbers for fine tuning? Pressures are a bit high and the variance L/R is a little too much. My remedy seems to be a couple of cranks on the left TB. Does that sound right?
and thanks a bunch for the cheat sheet you produced. Very helpful!
Hi,
I have an AHC issue with my '06LC. I read almost everything here, so started to become "experienced" in AHC maintenance:
Oil flush done, pump changed, techstream working, cross-level check done, front TB adjustment done, etc.
Actually I have a bad rear height sensor (most probably) I tried to save it, but 2 springs are broken, the carbon circuit looks quite bad, etc.
So I have to change it, but I am living/working in a country where there is no spare parts and shipping from abroad is risky.
Anyway:
one question to the members:
is there an option to skip the sensor and put the ECU in a safe mode? maybe disconnecting from the circuit ? and have a "normal" ride...
actually when I start the engine the rear goes up to 62cm (fender to hub) and bumping
and after 1-2km it goes down completely (44cm) and bump.
maybe if there would be a constant, for instance 2,5v signal from the rear sensor I would be able to use the car correctly until I change the sensor.
Any comment would be appreciated.
thx
I have an AHC issue with my '06LC. I read almost everything here, so started to become "experienced" in AHC maintenance:
Oil flush done, pump changed, techstream working, cross-level check done, front TB adjustment done, etc.
Actually I have a bad rear height sensor (most probably) I tried to save it, but 2 springs are broken, the carbon circuit looks quite bad, etc.
So I have to change it, but I am living/working in a country where there is no spare parts and shipping from abroad is risky.
Anyway:
one question to the members:
is there an option to skip the sensor and put the ECU in a safe mode? maybe disconnecting from the circuit ? and have a "normal" ride...
actually when I start the engine the rear goes up to 62cm (fender to hub) and bumping
and after 1-2km it goes down completely (44cm) and bump.
maybe if there would be a constant, for instance 2,5v signal from the rear sensor I would be able to use the car correctly until I change the sensor.
Any comment would be appreciated.
thx
Hi Guys.
I am putting in new AHC struts on rear of my 1998 LC 100.
I want to replace my rear sorings as well. I do use LC on a 10ft x 5ft tipping trailer.
So I am hoping someone can help me understand what would be the best new sorings to put in when I am doing the new hydraulic AHC struts.
Thank you.
I am putting in new AHC struts on rear of my 1998 LC 100.
I want to replace my rear sorings as well. I do use LC on a 10ft x 5ft tipping trailer.
So I am hoping someone can help me understand what would be the best new sorings to put in when I am doing the new hydraulic AHC struts.
Thank you.
Unless you always tow a trailer, I'd look into adding air bags. You can inflate and deflate as needed.
The spring that's right for towing is not likely right for driving without a trailer.
Thank you for your considered reply.
Unfortunately I have already committed to keeping the truck kitted with the original AHC system, having fitted 4 new AHC spheres recently and I have already bought the new AHC struts.
I do fully accept your suggestion is the ultimate answer but I feel im committed to having to stay with the original system.
This bring the case, I am looking for any suggestions on what would be the best springs to fit.
Toyota have 2 options, I’m not sure that both options fit my model. The two toyota options are Basically two different heights.
I believe they are colour coded.
Pink mark on spring is H 455
And the other is H 486.
I am assuming these are just height in millimetre figures.
So perhaps the taller spring would give more assistance to the AHC system!!
I can vaguely remember something about fitting spacers either on top or below the stock springs. But I’m not at all sure of the correct application with that idea.
To review,
I am looking guidance on what replacement springs to fit on my LC100 1998.
I am fitting two new AHC struts and I think it best to replace the springs at this time.
I use the truck to pull trailers on a semi regular basis.
Thank you to everyone. I appreciate any and all suggestions.
I think you're confused.
Keep the AHC, of course!
In addition to AHC, use air bags. They are used together as a complimentary system.
I am not suggesting you remove AHC. I rarely speak those words, haha.
