New poster here. I have been reading this forum for over a year which has been how long I have been trying to get my Auto Height Control issues resolved. I have done a ton of reading on troubleshooting. In a nutshell I began having issues where the front of the vehicle appeared to be in "HI" mode (while the light indicated it was in "N"). The ride was very bouncy and the truck doesnt seem to level out. Its as if the front of the truck is in HI all of the time. It does lower when in low but this appears to me to be the actual "N" position for the front. Through research I assumed it was a bad height control sensor. I have replaced all three height control sensors, doing first the front L, frontR, and the rear. and there was no improvement. The vehicle seems to "function" fine electronically in that it will raise and lower per the lights inside the vehicle and will return to "N" once the driving speed is reached. When the new height control sensors did not solve the problem I changed the AHC fluid, checked fuses, and relays to no avail. Recently I purchased 4 new globes/accumulators and installed them today. Unfortunately this did not solve the problem. The truck seems to think it is in "N" while the front is sitting in the "High" position. I have disconnected the battery and have cleared codes. I do not have tech stream. The Pump seems to run. My mechanic suggested installing the landcruiser (non AHC) suspension parts. I have 255,000 miles on the rig and love it. I want to keep the AHC. The local Lexus Dealer stated that they would not troubleshoot it and will install all new AHC parts/components for $4,500. I cannot afford this. Today after installing the globes if I put the vehicle in "low" the light blinks and the truck seems to lower but does not go to have a solid "L" light (continues to blink "L"). As a side note I had a weird occurrence within the last week. I was driving at about 20 miles per hour and the front left and right rear brakes seemed to activate for 1 or two seconds and it felt like the anti-lock brakes pumped ( I was not pushing the brake pedal). This was prior to installing the globes. I have also had the traction control beep at random while on dry roads at low speeds. This has not happened in some time. I have also had several dash lights come on at random and stay illuminated at startup and later go off. These weird instances seem to occur after it rains. My concern is the AHC, but could these things in their totality indicate some electrical problem related to/in conjunction with the issues with the AHC? If anyone has any advice for next steps I would greatly appreciate it. Can a wheel speed sensor impact the AHC? Thank You if anyone has advice. I have read it could be the leveling/gate valve assembly. I plan on checking and cleaning the connections tomorrow.
2004 Lexus LX470 AHC Help Needed (1 Viewer)
- Thread starter Howch
- Start date
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Step 1. Get Techstream.
Step 2. Use Techstream.
Summary: Techstream.
You really are just stabbing in the dark without having some means to pull the digital diagnostic data.
You need to verify pressures and sensor placements. None of which can be done without a means to read that data.
Techstream. Techstream and then more Techstream. It's free.
Step 2. Use Techstream.
Summary: Techstream.
You really are just stabbing in the dark without having some means to pull the digital diagnostic data.
You need to verify pressures and sensor placements. None of which can be done without a means to read that data.
Techstream. Techstream and then more Techstream. It's free.
- Thread starter
- #3
Thanks for your response. Can you provide your suggestion for where/how to obtain/purchase Techstream and the easiest way to utilize this for someone who has no experience with it? Perhaps a suggestion/weblink for products if you have this info readily available? I am somewhat computer savvy and have several older laptops that I can use. I just need to know what to get. I looked on Amazon but there are lots of mixed reviews and reports of compatibility issues. I have not been able to locate the free version. Thanks
Search this site for "Techstream in 5 minutes". It's all laid out, links, instructions and pages of misc troubleshooting help.
- Thread starter
- #5
Thank You!Search this site for "Techstream in 5 minutes". It's all laid out, links, instructions and pages of misc troubleshooting help.
Thread 'How-To: TechStream In 5 Minutes'
How-To: TechStream In 5 Minutes - https://forum.ih8mud.com/threads/how-to-techstream-in-5-minutes.1034923/
How-To: TechStream In 5 Minutes - https://forum.ih8mud.com/threads/how-to-techstream-in-5-minutes.1034923/
- Thread starter
- #7
So I am waiting on the Techstream cord to arrive from Amazon and I have installed the software. I decided to take a look at the car again today. Like I stated the front is riding super high and stiff. I could not adjust the ride height (It would just blink twice and stay in neutral). I decided to disconnect the battery. When I reconnected the battery it sounded like the AHC pump attempted to start/run on two occasions, then stopped, and then the AHC light "Off" started blinking. Now every time I start the vehicle it does this. It rides really rough-pogo stick. I am planning on using Techstream when I have it. Any suggestions for the next few days? Anyone know how I could lower the front of the vehicle so that it would be driveable? The rear seems fine but the front is super high. I drive a lot for work and have kids to drive to school. I'm considering buying some dynamite. Thanks
ramangain
Clarksonian disciple
You can PROBABLY improve the ride quality by adjusting the torsion bars so the AHC supports more weight, just for the time being. Have you even touched the torsion bars yet?
How did you set the new height sensors when you installed them? If you adjust the height sensors and then cycle through the height settings does the neutral height change? What are your actual neutral height measurements (hubcap center to fender) and how do they compare to the recommended measurements?
- Thread starter
- #10
I just measured the old height sensors and they appeared to be almost exact to the originals. To clarify. The front of the car started to be and stayed abnormally Hi over a year ago. I did some research at that time on this site. I first took apart the original sensors and cleaned them/checked springs-used pencil eraser, no help. Later and about a year ago I replaced all three sensors (one at a time) several weeks apart. No help. At that point the car would at times adjust from L to N to HI intermittently (on command- Sometimes worked sometimes wouldnt). It always seemed like the front was in a "HI" position when it showed to be in "N". I took the car to a local independent mechanic approx 10 months ago. He stated the pump checked out and according to him the sensors did not seem to be the issue. He suggested I install Landcruiser or Slee non AHC suspension, but also said he thought my globes were bad. The car had about 220,000 miles on it at that time and I had owned it beginning with about 80,000 miles. I hadnt done anything to the AHC over the course of ownership and it had worked perfectly. I have maintained the vehicle otherwise including timing belt, routine oil changes, etc. I was unaware of the specifics of the AHC system etc prior to it failing. During this time the car would occasionally return to a more neutral position in the front. At one point I pulled the AHC fuses on the driver's side kick panel to prevent the car from returning to the abnormal "Hi" position. It drove pretty good during this time and was not overly bouncy. Within the past few months I had the some extra cash and purchased the 4 globes (original Toyota/Lexus parts). I had the mechanic install them. I had replaced the fuses prior to this and the pump was running and the height control was working although the front was again HI and bouncy. When I scheduled with the mechanic to install the globes I spoke to and provided him with the Globe installation prodedures, bleeding requirements, etc per the instruction on this website. I has new fluid with the globe installation and had previously replaced the fluid per instructions on this site prior to getting the ride height sensors. After recently having the globes installed the front end was again very HI and bouncy. I had assumed it was the globes and now realize that I should have used Techstream or taken it to a mechanic that does.
So after having the globes installed recently and still having the bouncy ride, I wanted to see if I disconnected/reconnected the battery whether I could get the AHC to lower the front. My hope was that this would work and that I could again pull the fuses, and drive it until I have Techstream or have time to be without a car. After disconnecting the battery, when starting the car, I can hear the pump kick on for 1 second, kick off, kick on again, 1 sec and kick off, then the AHC light "Off" comes on, and the front remains skyward. I have been wondering if this was the pump all along, or the pressure sensor etc. The car is not really driveable right now as the front is sketchy Hi. I did try the active test for the pump using the engine compartment short and the controls inside of the car. During the test there appeared to be no response. Since the front is "Hi" I only tried to lower the front. I did not hear the pump at all during the active test. Thanks again for any advice. My Techstream cord should be here in 3 days. I am wondering whether Techstream will have much value now given these issues.
So after having the globes installed recently and still having the bouncy ride, I wanted to see if I disconnected/reconnected the battery whether I could get the AHC to lower the front. My hope was that this would work and that I could again pull the fuses, and drive it until I have Techstream or have time to be without a car. After disconnecting the battery, when starting the car, I can hear the pump kick on for 1 second, kick off, kick on again, 1 sec and kick off, then the AHC light "Off" comes on, and the front remains skyward. I have been wondering if this was the pump all along, or the pressure sensor etc. The car is not really driveable right now as the front is sketchy Hi. I did try the active test for the pump using the engine compartment short and the controls inside of the car. During the test there appeared to be no response. Since the front is "Hi" I only tried to lower the front. I did not hear the pump at all during the active test. Thanks again for any advice. My Techstream cord should be here in 3 days. I am wondering whether Techstream will have much value now given these issues.
- Thread starter
- #11
And thanks for the replies earlier I have not looked at the torsion bars or manually adjusted the sensors. I will attempt to do this tomorrow.
I honestly wouldn't touch anything right now.
Pulling fuses and resetting things isn't going to help. The system is very, very reliable. There aren't any typical electrical gremlins you can fix with power cycles.
I expect you'll find the sensors are way out of whack. To my knowledge you can't really install new sensors without Techstream. You need to set the new sensors based on their electrical output compared to the mechanical stance of the vehicle. Without Techstream, that's a chore. One that sounds unlikely to have happened.
Are the new sensors genuine Toyota/Lexus?
If the sensors are adjusted such that they read artificially low, the system will try to raise the car. When it can't raise (because the shocks are already fully extended) it will stop the pump and blink AHC.
I expect the ride to be terrible right now. The shocks sound like they're pegged at full extension.
Post up screen shots of the data fields once you get Techstream connected. It should be interesting, haha.
Pulling fuses and resetting things isn't going to help. The system is very, very reliable. There aren't any typical electrical gremlins you can fix with power cycles.
I expect you'll find the sensors are way out of whack. To my knowledge you can't really install new sensors without Techstream. You need to set the new sensors based on their electrical output compared to the mechanical stance of the vehicle. Without Techstream, that's a chore. One that sounds unlikely to have happened.
Are the new sensors genuine Toyota/Lexus?
If the sensors are adjusted such that they read artificially low, the system will try to raise the car. When it can't raise (because the shocks are already fully extended) it will stop the pump and blink AHC.
I expect the ride to be terrible right now. The shocks sound like they're pegged at full extension.
Post up screen shots of the data fields once you get Techstream connected. It should be interesting, haha.
- Thread starter
- #13
Ok Will do. Thanks for your time.
- Thread starter
- #14
Ok, a few things I did adjust the torsion bars and got the front down, it was still rough but better. This morning I removed and reinstalled the front height control sensors. I adjusted them (making them a bit longer). Reinstalled them and the car seemed to level itself when I started it. It drives pretty good now but sill flashes AHC off once its in gear. I just received my Techstream cable today and was able to connect it. I am aware that I have a lot to learn about using it and that the pressure test requires the removal of the sensor. I did not have time to do this. I did see that there were two error codes: C1712 Front Height Control Sensor LH Circuit Malfunction, and C1776 Front Wheels Speed Sensor Signal. The FR Height Control Sensor has a value of 0.2; The FL Height Control Sensor has a value of -6.3; RR Height Control Sensor has a value of -0.4. I cleared the codes via Techstream. Any advice of what to try to do first would be appreciated. Thanks
- Thread starter
- #15
What is the procedure to verify and adjust sensor placement or can you direct me to a page with this info? Thanks
ramangain
Clarksonian disciple
That FL HCS is probably toast. Swap FL and FR sensors to see if the error also moves corners (don't install, just electrically connect). If so, the sensor is kaput. If not, it could be a wiring issue connecting the FL to the AHC ECU.
That's what I'd try next.
That's what I'd try next.
- Thread starter
- #17
OK Thanks, the front left sensor is newer (less than a year old). That was the first thing I replaced. I suspected that was the issue initially but didnt install the new one using techstream. Is it possible that the code is from the original sensor?
The C1712 code STRONGLY suggests an open circuit in that wiring loom.
Glad to see you're doing ok @PADDO.
- Thread starter
- #20
Thank You
