(Not Solved Anymore :/) New year, new problems. 2004 LX470 is a rolling pogo stick.

[Chibu]

Ok, now that you have techstream:
How-To: TechStream In 5 Minutes

Then, your front heights look WAY off. It's far too high, and will most definitely ride like garbage.
Looks like either: your height sensors have failed, or they are set super wrong.

The "AHC Cheat Sheet" from @suprarx7nut, is outstanding, there's a good video as well.
AHC Info

Another good place to start is to read this:
Definitive list of AHC maintenance items

Get your heights (fender-hub) under control,adjust neutral AHC pressures & cross level, check H->L graduations, order replacement globes if required (sounds probable).

The system is pretty simple to work on once you figure out how., and it's worth the effort. Once you have it right, the ride is butttttttterrrrrrrryyyyy

Keep posting here, and ask for help as you need.

Thanks for the info. Makes me much more relaxed knowing I won't have to scour for every last bit of info and mash them all together and guestimate how the system works lol.

That loom just fell off into the bucket. No way that was in the hydraulic system.



Or maybe hook up Techstream, discover the obvious problem and spend a fraction of the time and money correcting the problem and keeping superior suspension?

Smart guy. Let us know what Techstream shows. Probably need new globes and new fluid, maybe a height sensor. All much less expensive than a conversion.

 

[ktmracer01]

If you're going to be draining the fluid and removing any parts of the AHC, buy some fresh AHC fluid. YOu do not want to be re-introducing potentially contaminated fluid back into the system. No matter how many times you filter it, you'll never remove 100% of the contamination, and/or moisture from what is bled out of the system.

Agreeing with everyone else, you need to Tech Stream and follow the FSM guidance on checking the health of your AHC system. I've worked on the AHC systems a lot in the last couple of years, and more often there is usually a very simple fix to an AHC system that is acting up.

Unfortunately, most dealerships ( or general mechanics) have very few people that are familiar enough with the AHC system to work on it and also made the cost of maintenance soo high on the AHC that most vehicle owners decide not to have maintenance done. We're hitting 20+ years on a lot of these rigs and unless the owners were diligent in maintenance, we're going to see more and more of them need some type of work.

 

[SemperRex]

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

forum.ih8mud.com

This is another great thread for all things AHC

 

[Chibu]

Well semi-update. Like 2 weekends ago I re-changed out the crap "used" CV Axle on the driver side for a dealer-bought OEM axle and I remembered to put in the ABS sensor this time and so there aren't any more axle popping woes and the ABS, VSC, and AHC systems, based on the lights on the dash (or the lack thereof), should be working properly. But of course, nothing must ever work as it should. Went to put the car into the HI position and it just consistently blinked and did nothing. Fuse issue?

Regardless, I finally got the Mini-VCI cable and it doesn't seem to be working. I plug it into the car and then into my computer and the computer registers that it has been connected. Maybe I'm stupid but is there a device driver I will need to install for the cable? (There is, fact check true: I am stupid). As it stands now, Techstream isn't recognizing the car with the cable connected. The cable came with a disc supposedly loaded with techstream, but alas, when I put the disc into my computer, it does a great summary of absolutely nothing. and it only decides to work when I put it into my mom's computer. Well time to go back outside and keep ****ing around with the car until the battery dies again. Hopefully this $35 won't go to complete waste.

Quick note for now: the front suspension hits bump stops when coming down from a speed bump. I think there isn't any fluid in the front shocks (because it was all drained out when I went to inspect the front globes) but there is some damping because accumulators, and even though the AHC system is apparently fine~ish now (it still blinks OFF on random drives, i.e. you start the car and drive 10 miles and it doesn't blink OFF, then you park, completely shut the car off, start it up again, and start driving, and within seconds it will blink OFF and continue for most of the trip) it still seemingly hasn't pumped fluid into the front shocks. Rear seems to be sitting at normal height but it may be in high, will measure later in the evening.

P.S. Also haven't had that weird pogo stick issue since properly installing the ABS sensor (which enabled the AHC system to function again). It was the catalyst for this thread but I guess it's on the back burner now, seeing as that issue is (hopefully) gone (knock on wood) and the main direction of the thread is to fix the AHC system as a whole or at least figure out wtf is wrong with it.

 

[Chibu]

Went to put the car into the HI position and it just consistently blinked and did nothing. Fuse issue?......Quick note for now: the front suspension hits bump stops when coming down from a speed bump.

Small update to these in my previous post. The car doesn't hit bump stops on all rides (a ride being a full drive cycle, i.e. start the car, drive around, shut the car off completely); some rides, the front suspension actually works normally and other rides it hits bump stops as if there is no fluid in the front shocks. Also, on rides where the front suspension is working normally, if I try to put the car into high, rather than blinking pointlessly on end, it either blinks twice and does nothing, or the OFF light starts blinking. Well, summary is, imma load up Techstream first thing in the morning.

 

[Chibu]

Finally got Techstream going. Read AHC Trouble Codes and came back with one code: "C1712 Front ride height sensor LH malfunction." Then I read the data list:

According to The ABCs of AHC, my height sensor and pressure sensor readings are way off. sigh
I know I'm meant to be cycling through the different vehicle heights as I measure this, but of course, the height switch does nothing (and is to be replaced) and I'm not too confident with messing with the pins. And even then, when messing with the pins to (attempt to) put it into HI (after storing and clearing the C1712 trouble code) the HI light on the dash was just blinking on end with no change in vehicle height, all while the pressure sensor readings were still a solid and astounding 0.

 

[2001LC]

You need to put in H, than L than N, than look at reads in Tech stream. So without getting AHC to work (go up and down), you can't make anything of Mpa readings.

Make sure it has fluid in reservoir.

Cross (Side to side) level vehicle. Turn Torsion-bar 30mm adjusting bolt clockwise (CW) on low side to cross level. Than turn each T-bar adjuster bolt 5 or more CW turns each. This puts more weight on T-bars and takes weight off AHC system. Excessive weight on AHC, fluid gets to hot and fails as you drive. This may be why works for short drives (heats as you drive), then fails.

Make sure engine running, and all doors close when raising or lowering with AHC.
Make sure on level ground when taking tech stream reading, and to measurements (fender to axle) to cross level.

Note: The 6.7 inch FL. That is front left sensor. Make sure to look all all sensor closely, especially the FL. The sensor arm ball joints, are freezing causing damage.

 

[Chibu]

You need to put in H, than L than N, than look at reads in Tech stream. So without getting AHC to work (go up and down), you can't make anything of Mpa readings.

Make sure it has fluid in reservoir.

Cross (Side to side) level vehicle. Turn Torsion-bar 30mm adjusting bolt clockwise (CW) on low side to cross level. Than turn each T-bar adjuster bolt 5 or more CW turns each. This puts more weight on T-bars and takes weight off AHC system. Excessive weight on AHC, fluid gets to hot and fails as you drive. This may be why works for short drives (heats as you drive), then fails.

Make sure engine running, and all doors close when raising or lowering with AHC.
Make sure on level ground when taking tech stream reading, and to measurements (fender to axle) to cross level.

Note: The 6.7 inch FL. That is front left sensor. Make sure to look all all sensor closely, especially the FL. The sensor arm ball joints, are freezing causing damage.

Will see what I can do. For now I can't put the car into anything other than "N" because the AHC refuses to function. Also, the AHC doesn't actually fail the longer the drive is. It either fails (i.e. the OFF light begins to blink) after the first few feet of moving, or it works the whole drive (and vice versa). Fluid in the reservoir is intact.

Also, I live near the equator and I WISH I could get outside temps anywhere near cold enough to freeze anything. Summer has just arrived (we don't have winter but instead a dry season which is basically summer without rain) and it is HOT and humid. My brother actually has a saying about where we live: The country is hot, and the people are hostile.

 

[Chibu]

Ok guys. The investigation continues. Not sure if I should make a new thread for this now or not lol. For posterity, all tests were carried out (and all screenshots taken) when the car engine was running.

Well, I went out and hooked up Techstream, read AHC Codes and the C1712 code was back:

Given that the code came back after I last cleared it and the car had gone through a full cycle of working for a second and then not working again, the driver side sensor might be suspect.

Well, nevertheless, I cleared the code and read the data list for the AHC system:

Well this time the front height and pressure sensors were reading something and when the car was moving, I could see the height and pressure sensors changing and the step values for front and rear were also changing. Also take not how the IG and +B (AHC IG and AHC B fuses I would assume) have sufficient current.

That's all well and good. Now, I read on another thread were OP was experiencing similar issues, that the issue could be the ECU IG not getting current. OP claimed that he checked the data list of the ABS/VSC section and saw the ECU IG (presumably shown as "IG VOLTAGE" in my pic below) was reading "too low," so I followed suit and checked that and mine came back "normal":View attachment 2953023

Well I had conflicting feelings about this, but I trudged on.

I then checked ABS/VSC codes because I know that the ABS/VSC and AHC systems work brake-in-shocks ():View attachment 2953022

I disregarded all these codes because just some weeks ago I re-installed the front speed sensor after leaving it unplugged for months which stopped the ABS and AHC systems from functioning. And also some weeks ago we had an issue where the rear right brake caliper seal was leaking fluid everywhere. In any case, I cleared the codes and after a few rounds of driving (will get to later), they didn't come back and no lights are present on the dash (none were present prior to clearing the codes either). As soon as I cleared these codes (or a few moments later), the AHC OFF light came steady on the dash, suspicious, but ok.

So at this point, the front of the car is low to the ground, the fender is 17.5 inches from the center of the wheel (as opposed to 19.5), the C1712 code is n longer reading on the AHC system. I turned off the car completely, waited a few, started it up, still no code. Great. So I go for a drive with the AHC OFF light steady on the dash. Not up to 15 meters to get out of my driveway and into the road and the OFF light is gone. Not blinking, GONE. So I was like, "yeah, sure," and drove around the neighborhood, and, of course, the light came back but blinking this time. I think 1 blink per second. So I am coming back and it's still blinking, get close to my driveway, still blinking, stop looking at it because I figure it will just keep blinking. Well, I stop, park. And it's not blinking. Smh. Get out of the car and the front is at the correct height, the fender is exactly 19.5 inches from the center of the wheel (as opposed to 17.5 inches when it's low). The rear is also 20.5 inches so that's good. All measurements were taken on level ground. Well great. I check for codes, no codes. I go out again, the OFF light doesn't blink, get back home, OFF light isn't blinking, get out of the car, and the front is back down to 17.5 inches. Wtf?!

Here's an image of the wheel-to-fender gap when the height is normal and correct:

IMG-20220315-163647-607 hosted at ImgBB

Image IMG-20220315-163647-607 hosted in ImgBB

ibb.co

Here are images of the wheel-to-fender gap when the height is low in the front (for some unknown reason) along with a close up of the tape measurement:

IMG-20220315-165334-608 hosted at ImgBB

Image IMG-20220315-165334-608 hosted in ImgBB

ibb.co

IMG-20220315-165554-614 hosted at ImgBB

Image IMG-20220315-165554-614 hosted in ImgBB

ibb.co

And yes, there is fluid in the reservoir, as shown by this pic of the fluid level when the front height was normal:

The fluid is smack between max and min. When the front goes low, the fluid rises up to that midpoint that looks like a joining between the upper half of the container and the lower half (the fluid level is way above max).

Also I think it must be noted that the original 10mm nut connecting the Front Left height sensor (the one throwing codes) linkage to the sensor fell into the lower control arm last year when I was changing the CV Axles and I used another 10mm nut (slightly different design, had a built in washer, and also looked like brass(?)) with the pre-existing washer to re-couple the linkage to the sensor. Maybe that's what's causing issues?

I am almost at my end. The next thing I plot to do is go disconnect the battery and/or the AHC IG and AHC B fuses and see what's what after that.

Any suggestions, or leads I could follow up on? I don't wanna mess with torsion bars just yet because this seems like some partial contact issue where the system works for a sec and then stops working again. What do I do?

 

[SemperRex]

Weird height sensor readings will cause the system to react weirdly.

Try cleaning the contacts on the height sensors.

 

[Chibu]

Noted. Will get around to that.

 

[GTV]

Front left height sensor is bad. You can try to clean it up but it's doubtful that will work. I'd get a new one and flush the system if you haven't already. Rear pressure is also a bit high, some 30mm coil spacers will correct that.

 

[2001LC]

While AHC working, Engine on doors closed. Raise to H, than lower to L, (wait for pump to stop and light to stop blinking, before next move up or dn). Than bring back up to N, and get a screen shot of AHC data after pump off & light stops blinking, wait 30 second to read data. Repeat test a few times. You should see accumulator ~10.5Mpa.

In your above picture of this, there's no Accumulator Mpa. Front Mpa is way to low at 2.2 mpa. This may be a false reading. Either false/bad reads form not going up, dn and ending at N. Or glitch in tech stream. Or a sensor failure, Are just 3 first things come to mind.

These may be actually reads, which could mean you've torsion bar way to cranked up (CW turns), for one.

We do keep seeing FL heights way off. last shows 5.5 inch. You also had a DTC indicating FL. Front drooping due to a sensor failure, could put most all weight on T-bar. Than you also get a very low Mpa front.

1. You may have it way out of adjustment. Post picture of every sensor, may help?
2. You may have a frozen adjustor arm, May even have bent!
3. You may have a damaged sensor.
4. You may have a wiring issue (back trace it, from sensor)

 

[Chibu]

Front left height sensor is bad. You can try to clean it up but it's doubtful that will work. I'd get a new one and flush the system if you haven't already. Rear pressure is also a bit high, some 30mm coil spacers will correct that.

I'll try to clean it up and see what's what.

While AHC working, Engine on doors closed. Raise to H, than lower to L, (wait for pump to stop and light to stop blinking, before next move up or dn). Than bring back up to N, and get a screen shot of AHC data after pump off & light stops blinking, wait 30 second to read data. Repeat test a few times. You should see accumulator ~10.5Mpa.

In your above picture of this, there's no Accumulator Mpa. Front Mpa is way to low at 2.2 mpa. This may be a false reading. Either false/bad reads form not going up, dn and ending at N. Or glitch in tech stream. Or a sensor failure, Are just 3 first things come to mind.

These may be actually reads, which could mean you've torsion bar way to cranked up (CW turns), for one.

We do keep seeing FL heights way off. last shows 5.5 inch. You also had a DTC indicating FL. Front drooping due to a sensor failure, could put most all weight on T-bar. Than you also get a very low Mpa front.

1. You may have it way out of adjustment. Post picture of every sensor, may help?
2. You may have a frozen adjustor arm, May even have bent!
3. You may have a damaged sensor.
4. You may have a wiring issue (back trace it, from sensor)

The AHC refuses to go out of N. I have tried multiple times to put it into LO or HI but it either blinks twice and does nothing or blinks continuously and does nothing. Torsion bar hasn't been touched since the AHC was last working fine and all those screenshots above were taken when the front suspension was drooped down. It's looking more and more like that sensor may have gone out or is trying to.

 

[2001LC]

Does sound like sensor.