LX570 AHC “Basics” - Added as sticky thread for AHC Issues (11 Viewers)

[TeCKis300]

I wonder if it’s a model to model variation. There have been at least a few different revisions of the suspension ECU.

Looking at the following document, between the model years, the verbiage is the same. So who knows...

SUSPENSION CONTROL: ACTIVE HEIGHT CONTROL SUSPENSION: SYSTEM DESCRIPTION; 2007 - 2011 MY LX570
SUSPENSION CONTROL: ACTIVE HEIGHT CONTROL SUSPENSION: SYSTEM DESCRIPTION; 2016 - 2021 MY LX570

 

[nwfl4runner]

Well I've got the accumulators ordered from ebay and am in the process of ordering the new front shocks from a Lexus dealer in Georgia. Has anyone changed out the Upper Shock Mount bushing as part of this process? Is it pretty easy to do while the shocks are off? I can get each bushing for around $50. Part number - 9094801097

9094801097 - Lexus Suspension Shock Absorber / Strut Mount | Jim Hudson Lexus Augusta, Martinez GA

Genuine Lexus Part # 9094801097 (90948-01097) - Suspension Shock Absorber / Strut Mount Bushing (Left, Right, Front). FRONT SHOCK ABSORBER, NO. 1 LEFT; FRONT SHOCK ABSORBER, NO. 1 RIGHT. Fits LX 570. Ships from Jim Hudson Lexus Augusta, Martinez GA

parts.augustalexus.com

yes because changing the shock requires disassembling the entire unit

 

[joesrcool]

Alright, I have an update on the issues I was having and the easy way they all seemed to be resolved. To refresh everyone on what was done since I purchased the vehicle a month ago, I played with the height settings to see what type of sensor lift I could get and then lowered it back down to the factory recommended settings and I completed a full AHC fluid flush.

Symptoms experienced:

1. Stuttering when raising lowering
2. Side-to-side movement when raising lowering
3. Vehicle would sit and drive uneven for periods at a time, unable to duplicate upon command, this would cause the steering wheel to be off-center
4. Vehicle would not enter "LO" 9 out of 10 attempts
5. When transitioning from "HI" to "N" vehicle would lean almost every time
6. Vehicle would ride smooth immediately after startup, then after slowing from highway speeds, ride would be very harsh until next startup
7. I did finally get an AHC code on the dash when trying to lower and raise back up, light went away upon restarting the vehicle
8. Sporadic side-to-side height adjustments when sitting idle or at stoplights

I was able to borrow a Techstream cable from another local Toyota guy, so I booted it up and found the only stored code. Still not too sure why I got it, verified fluid is above max line and ensured oil pressure was within spec when raising (L to N: spec is 8MPa, actual 7.95; N to H spec is 13MPa, actual 12.31). Code was cleared and has yet to return after dozens of cycles to the system.

Stumped as to why there were no other codes, I looked at the data table to see if anything looked "off". Here is a screenshot of my data table before conducting any adjustments. I also remembered there was a note to calibrate the Vehicle Stability Control System any time there are height-adjustments made at the sensors. The G sensors readings looked a little off, especially the Back&Forth reading. There also seemed to be a bit of side-to-side discrepancies in the height readings as well. This got me to thinking, I wonder if the truck is confused as to where its at, with the G sensor and height settings trying to fight over where to set the truck's height.

Anyways, I thought it wouldn't hurt to conduct a calibration of the VSC system and a height adjustment calibration. I found the most level parking lot in the area and measured the vehicle height multiple times to ensure it was correct. Per the FSM, front height offset is spec'd at 101mm +/-8mm, my FL was 103 and FR was 106. Rear height offset is spec'd at 94mm +/-8mm, my RL was 94mm and RR was 90mm. I probably could have adjusted the sensors a bit more to get it a little bit closer to level, but they were within spec. I used those measurements for the height adjustment calibration and I figured the truck now knew where it was sitting at all four corners. Calibrating the VSC system was simple, just follow the instructions in the FSM. Below is the data list after adjusting and calibrating.

After completing those two simple tasks, all of my above symptoms went away. As you can see, left to right height is much more even and the Back&Forth G sensor is zero'd out. I've cycled the system dozens of times since doing this, and everything works as it should, but even smoother and faster. I have yet to experience any of my previous symptoms since doing this, and I'm comfortable with call these issues resolved.

The one thing I'm curious about and haven't had much luck finding, is the steering angle reading. The vehicle tracks perfectly straight and the little picture in the screen shows the correct orientation of the front wheels, but it seems like this should be reading 0.

 

[grinchy]

Alright, I have an update on the issues I was having and the easy way they all seemed to be resolved. To refresh everyone on what was done since I purchased the vehicle a month ago, I played with the height settings to see what type of sensor lift I could get and then lowered it back down to the factory recommended settings and I completed a full AHC fluid flush.

Symptoms experienced:

1. Stuttering when raising lowering
2. Side-to-side movement when raising lowering
3. Vehicle would sit and drive uneven for periods at a time, unable to duplicate upon command, this would cause the steering wheel to be off-center
4. Vehicle would not enter "LO" 9 out of 10 attempts
5. When transitioning from "HI" to "N" vehicle would lean almost every time
6. Vehicle would ride smooth immediately after startup, then after slowing from highway speeds, ride would be very harsh until next startup
7. I did finally get an AHC code on the dash when trying to lower and raise back up, light went away upon restarting the vehicle
8. Sporadic side-to-side height adjustments when sitting idle or at stoplights

I was able to borrow a Techstream cable from another local Toyota guy, so I booted it up and found the only stored code. Still not too sure why I got it, verified fluid is above max line and ensured oil pressure was within spec when raising (L to N: spec is 8MPa, actual 7.95; N to H spec is 13MPa, actual 12.31). Code was cleared and has yet to return after dozens of cycles to the system.
View attachment 3032585

Stumped as to why there were no other codes, I looked at the data table to see if anything looked "off". Here is a screenshot of my data table before conducting any adjustments. I also remembered there was a note to calibrate the Vehicle Stability Control System any time there are height-adjustments made at the sensors. The G sensors readings looked a little off, especially the Back&Forth reading. There also seemed to be a bit of side-to-side discrepancies in the height readings as well. This got me to thinking, I wonder if the truck is confused as to where its at, with the G sensor and height settings trying to fight over where to set the truck's height.
View attachment 3032589

Anyways, I thought it wouldn't hurt to conduct a calibration of the VSC system and a height adjustment calibration. I found the most level parking lot in the area and measured the vehicle height multiple times to ensure it was correct. Per the FSM, front height offset is spec'd at 101mm +/-8mm, my FL was 103 and FR was 106. Rear height offset is spec'd at 94mm +/-8mm, my RL was 94mm and RR was 90mm. I probably could have adjusted the sensors a bit more to get it a little bit closer to level, but they were within spec. I used those measurements for the height adjustment calibration and I figured the truck now knew where it was sitting at all four corners. Calibrating the VSC system was simple, just follow the instructions in the FSM. Below is the data list after adjusting and calibrating.
View attachment 3032596

After completing those two simple tasks, all of my above symptoms went away. As you can see, left to right height is much more even and the Back&Forth G sensor is zero'd out. I've cycled the system dozens of times since doing this, and everything works as it should, but even smoother and faster. I have yet to experience any of my previous symptoms since doing this, and I'm comfortable with call these issues resolved.

The one thing I'm curious about and haven't had much luck finding, is the steering angle reading. The vehicle tracks perfectly straight and the little picture in the screen shows the correct orientation of the front wheels, but it seems like this should be reading 0.

Nice work!

 

[Raj]

Hi Everyone,
Since this thread is about AHC basics I thought I will request advice on this thread instead of a new one.
Mine is 2014 200 series. I am doing AHC flush process from the instructions I printed out a while ago from here. It started with just bleed but ended up in flush so what I did a slightly modified way. Instead of taking out fluid from the reservoir, I just filled it to the top, bleed 4 sides, fill again and repeat the process. Until now I used up 3 liters. Will continue the process until I add all 5 litres in and take out 5 litres.
In the instructions, it was clearly mentioned not to mess with the 5th bleed valve and just carry on with the 4, one on each side.
Any idea why we are not supposed to bleed the 5th one? Will there be any improvement in the ride if I try and bleed some air out of the 5th one as well?

 

[Raj]

I didnt touch the 5th bleeding valve (accumulator? behind the shield) and closed this process. I used up more than 4 litres AHC (fill reservoir to max, bleed 4 valves, start car run through L,N,H and repeat the process again). Attached image of pure AHC and the one from the last bleeding.
Will the colour of the one coming out of one of the bleeding valves be the same as pure AHC or will it be slightly different? Do we have to run AHC fluid until the fluid coming out of bleeders matches the reference colour?

 

[JS22STL]

Completed the AHC flush on mine at 50k miles. The fluid was extremely brown. The process is super easy. Anyone with a little patience and 2 hours can do a complete flush. I bled each one twice until the fluid came out clean. Ran through 2 metal cans of AHC fluid.

 

[turbotwo]

New to the thread, new 200 series owner (2010 LX). My truck has 140k miles on it, and has had the fluid flushed at the dealer in 2014 at 87k miles. The seller also indicated he did it himself once more a few months ago. I'm getting a check AHC light and getting code C1755 Rear Gate Valve on Techstream. I haven't noticed any leaks but plan to do a more thorough inspection. Any other advice on what to check in order to diagnose the issue? Thanks.

Just to update, I took no action other than some visual inspection and wasn't able to sort the problem, however the vehicle was driving fine. The check AHC light would come and go, and when it was off the AHC worked just fine.

Now though I have a C1763 code and the AHC is stuck on Low. If I clear the code it comes right back. When I checked the level of the fluid I couldn't see the line, so it was either empty or way too full. I siphoned a full whisky bottle out, and now it's reading a little higher than max. Which is probably about right given how low the vehicle is sitting. Code is still showing and comes right back after clearing. I guess the next step is to bleed the system to ensure there's no air in it?

 

[turbotwo]

Also a follow up question, what's the generally accepted best order of operations for bleeding the fluid? Also can I even bleed it properly if I can't run the pump to get it back up to normal height?

 

[LXGus]

Loads of great info in here! I'm about ready to try my first flush and was thinking of going with PADDO's method, but I do have a few questions:

1. What affordable tools are you using to draw the old fluid out of the reservoir?
2. I see a bunch of images of a clear tube with a lid screwed onto a clear plastic bottle for the old fluid to drain into, where do you get that?
3. if drawing fluid out of the reservoir is a challenge, is there a method that new fluid is poured into the reservoir as the old fluid leaves it, or does this mix too much fluid?
4. I was able to purchase the last 2.5L can from the dealership. He said it should but plenty, but others are saying I need more than 2.5L. PODDO's method uses the full 2.5L can, but I can't tell if it's for a 100 or 200 - not sure if the two trucks use different amounts of fluid

 

[tbisaacs]

Loads of great info in here! I'm about ready to try my first flush and was thinking of going with PADDO's method, but I do have a few questions:

1. What affordable tools are you using to draw the old fluid out of the reservoir?
2. I see a bunch of images of a clear tube with a lid screwed onto a clear plastic bottle for the old fluid to drain into, where do you get that?
3. if drawing fluid out of the reservoir is a challenge, is there a method that new fluid is poured into the reservoir as the old fluid leaves it, or does this mix too much fluid?
4. I was able to purchase the last 2.5L can from the dealership. He said it should but plenty, but others are saying I need more than 2.5L. PODDO's method uses the full 2.5L can, but I can't tell if it's for a 100 or 200 - not sure if the two trucks use different amounts of fluid

I used a cheap transfer pump and a brake bleeder with container

 

[Raj]

first flush

I tried for the first time and didn't have the proper tools to empty the reservoir so I just filled it to the top, bled all valves, and repeated the process until I used up 4 liters of new fluid until I could see clear fluid and color change close to a fresh one. Not sure if this method will be as good as proper flush. Also, I didn't bleed or flush the AHC accumulator as its behind the metal shield and I have to go under the car. Was not sure if the car will come down by bleeding this one so left the AHC accumulator and just did 4 corners.

 

[LXGus]

I tried for the first time and didn't have the proper tools to empty the reservoir so I just filled it to the top, bled all valves, and repeated the process until I used up 4 liters of new fluid until I could see clear fluid and color change close to a fresh one. Not sure if this method will be as good as proper flush. Also, I didn't bleed or flush the AHC accumulator as its behind the metal shield and I have to go under the car. Was not sure if the car will come down by bleeding this one so left the AHC accumulator and just did 4 corners.

I’ve read the car does not lower when flushing the AHC accumulator but obviously I have no experience, yet.

 

[lx200inAR]

I’ve read the car does not lower when flushing the AHC accumulator but obviously I have no experience, yet.

The accumulator will not lower the vehicle. I believe all of Paddo’s advice is based on 100 series. You’ll need a thinner tube to recover old fluid from the reservoir. It’s not as easy as on the 100.

 

[Raj]

as easy as on the 100

If the car dosent lower, I will give it a try but I will get it up the ramps and try it. It's not easy to reach it. There is a metal shield on the passenger side in the middle tucked away from vision. I ve to open that shield to be able to view the accumulator assembly. I will share my experience after I try this accumulator bleed.

 

[Raj]

Finally did the AHC accumulator bleed/flush. This was easier than I thought. Just opened the bleeder until all the fluid was drained, added about a litre into the AHC reservoir tank and switched on the car and cycled through L,N,H settings.

 

[turbotwo]

Quick question, is this the correct method to manually power the AHC pump on the vehicle? Obviously the other ends are connected to a spare battery, and when I touch my multimeter leads to the back of the alligator clips it confirms 12v. If my pump isn't running in this configuration, is it dead?

 

[ROMR NTX]

My ride is not quite right and it seems to have come on suddenly. It will maintain heights ok, a little slow to move. But the damping is off, it blows through travel on dips, sometimes giving the feeling of hitting the bump stops.

No lights on the dash and no codes on techstream.

2013 with 85k miles. I bought it with 72k, the dealer records show a fluid swap on schedule, but the fluid is really dark. Time for new globes and fluid?

 

[radman]

Time for new globes and fluid?

seems premature for globes. Could be as simple as needing a good flush - i would start with that. However, i'm not sure how fluid could cause "sudden" changes to ride

 

[lx200inAR]

My ride is not quite right and it seems to have come on suddenly. It will maintain heights ok, a little slow to move. But the damping is off, it blows through travel on dips, sometimes giving the feeling of hitting the bump stops.

No lights on the dash and no codes on techstream.

2013 with 85k miles. I bought it with 72k, the dealer records show a fluid swap on schedule, but the fluid is really dark. Time for new globes and fluid?

Mileage wise, the globes are probably okay-ish. But seems like age in this case would be as important as anything else. I wouldn't rule out globe replacement. Especially if you possibly blew one and that's why your ride is significantly worse now. Definitely sounds like something is wrong if you had a large change in damping. If you are in sport mode, do you get the same wallowing in dips?