(SOLVED) A unique LX470 AHC issue: Ignition? (1 Viewer)

[BW100]

After searching endlessly for someone with the same AHC issue, I’ve finally decided to throw it out there and see if anyone has a solution.
2006 LX470, ~90k miles, owned since 2021. Wife’s daily driver.

AHC selector has been non responsive since prior to our ownership. No joke, here is the daily procedure:
-Turn ignition to “ON” (but do not start). After approximately 5 seconds, ride height will LOWER roughly .5”.

- Turn ignition to START, i.e., crank the truck: after approximately 5-10 seconds, the AHC system will RAISE the height by about .5”.
It also seems to successfully level out the front and rear.

As you can probably surmise, if one goes about their day running errands, (assuming you start the vehicle 6 times) you may arrive home 3” higher than when you left. When it gets too high, you just turn the key to ON, let it drop .5” at a time. Turn the key ON, let it drop, turn it off, repeat until at desired lower height.

While we’ve somehow managed to make this work, and for the most part we have: nonetheless, it’s definitely taking a toll on the front tires by way of inconsistent alignment.

3 years ago, I flushed the AHC system with no changed results. I also replaced the relay in the engine bay fuse box. Again, no change.

If anyone knows how the ride height could possibly be changing with the turn of the ignition key, please chime in. Again:
Key ON: ~ .5” LOWER
Key START: ~ .5” RAISE

No response from the AHC selector switch. The simple answer would be to replace the switch to see if it resolves the issue, but I’m curious if the switch goes out, how does the height control then move to the ignition switch?

Update: after running Techstream, here’s the data generated along with the current error codes:

 

[Bisho]

Interesting. Have you looked to see if there are any pending codes? Have you hooked up Techstream or something similar and checked pressures, or done the AHC setup in the "ABCs of AHC" thread? Have you checked the height sensors to make sure they are tight and not moving around? @suprarx7nut

 

[BW100]

Interesting. Have you looked to see if there are any pending codes? Have you hooked up Techstream or something similar and checked pressures, or done the AHC setup in the "ABCs of AHC" thread? Have you checked the height sensors to make sure they are tight and not moving around? @suprarx7nut

I have not hooked up a Techstream or any other diagnostic tool to check for codes, simply due to not having one. I feel positive there would certainly be some codes shown. However, besides the 2006 LX, I’ve owned a 2004 100 series LC for 8 years now, and there’s never once been an issue that I couldn’t find at least one other person with the same, along with the solution. This one seems to be totally one-off.

If we could simply get it to stay in the “N” height setting, we’d be happy. But the “OFF” button on the AHC doesn’t seem to function either. As far as replacing the switch goes, I’ve learned a long time ago not to start blindly replacing parts on a Toyota when there’s a problem. The issue (usually) is something far more simple.

 

[suprarx7nut]

After searching endlessly for someone with the same AHC issue, I’ve finally decided to throw it out there and see if anyone has a solution.
2006 LX470, ~90k miles, owned since 2021. Wife’s daily driver.

AHC selector has been non responsive since prior to our ownership. No joke, here is the daily procedure:
-Turn ignition to “ON” (but do not start). After approximately 5 seconds, ride height will LOWER roughly .5”.

- Turn ignition to START, i.e., crank the truck: after approximately 5-10 seconds, the AHC system will RAISE the height by about .5”.
It also seems to successfully level out the front and rear.

As you can probably surmise, if one goes about their day running errands, (assuming you start the vehicle 6 times) you may arrive home 3” higher than when you left. When it gets too high, you just turn the key to ON, let it drop .5” at a time. Turn the key ON, let it drop, turn it off, repeat until at desired lower height.

While we’ve somehow managed to make this work, and for the most part we have: nonetheless, it’s definitely taking a toll on the front tires by way of inconsistent alignment.

3 years ago, I flushed the AHC system with no changed results. I also replaced the relay in the engine bay fuse box. Again, no change.

If anyone knows how the ride height could possibly be changing with the turn of the ignition key, please chime in. Again:
Key ON: ~ .5” LOWER
Key START: ~ .5” RAISE

No response from the AHC selector switch. The simple answer would be to replace the switch to see if it resolves the issue, but I’m curious if the switch goes out, how does the height control then move to the ignition switch?

That's real strange. Sounds like a wiring fault - perhaps related to the fuse box.

I would work on getting Techstream hooked up and explore a bit there. I imagine you've got a code. The system should disallow the raised height at speed, so something is clearly wrong. Techstream might give you an easy answer.

 

[suprarx7nut]

I have not hooked up a Techstream or any other diagnostic tool to check for codes, simply due to not having one. I feel positive there would certainly be some codes shown. However, besides the 2006 LX, I’ve owned a 2004 100 series LC for 8 years now, and there’s never once been an issue that I couldn’t find at least one other person with the same, along with the solution. This one seems to be totally one-off.

If we could simply get it to stay in the “N” height setting, we’d be happy. But the “OFF” button on the AHC doesn’t seem to function either. As far as replacing the switch goes, I’ve learned a long time ago not to start blindly replacing parts on a Toyota when there’s a problem. The issue (usually) is something far more simple.

Wise man.

Hook up Techstream. AHC is complex enough that without the diagnostic tool, you're blind. It's not so crazy once you have that software, but it's pretty rough without.

 

[BW100]

That's real strange. Sounds like a wiring fault - perhaps related to the fuse box.

I would work on getting Techstream hooked up and explore a bit there. I imagine you've got a code. The system should disallow the raised height at speed, so something is clearly wrong. Techstream might give you an easy answer.

Wise man.

Hook up Techstream. AHC is complex enough that without the diagnostic tool, you're blind. It's not so crazy once you have that software, but it's pretty rough without.

Wise man.

Hook up Techstream. AHC is complex enough that without the diagnostic tool, you're blind. It's not so crazy once you have that software, but it's pretty rough without.

If I did hook up Techstream, could it potentially give me an obvious answer like “AHC switch is bad”? I’ve seen mechanics use it, but never have myself.

 

[suprarx7nut]

If I did hook up Techstream, could it potentially give me an obvious answer like “AHC switch is bad”? I’ve seen mechanics use it, but never have myself.

Not quite in those words, but it can give you breadcrumbs which lead to an answer.

If you have fault codes for a bad height sensor and bad height readings, you'll know in about 30 seconds that you need a new height sensor and which one.

There's no guarantee it will give you an easy answer, but it's at least where you should start.

 

[BW100]

Not quite in those words, but it can give you breadcrumbs which lead to an answer.

If you have fault codes for a bad height sensor and bad height readings, you'll know in about 30 seconds that you need a new height sensor and which one.

There's no guarantee it will give you an easy answer, but it's at least where you should start.

I’m sure the Techstream could provide useful hints, but what I’d really like to know is if anyone knows of any correlation whatsoever between AHC and the ignition? Even using the ignition ON/START workaround, the truck maintains level, front to back and left to right. I assume in a normally functioning 470, turning the ignition key has no effect whatsoever on the ride height. Mine’s never become stuck in a position; it can always be raised or lowered with the key…as crazy as that sounds.

*It can lower with the drivers door open or closed.
However, it will only raise (once the ignition is started) with the drivers door shut.

 

[Rhetoric]

You are throwing darts with a blindfold on without hooking up Techstream and investigating. It could literally be anything.

 

[BW100]

You are throwing darts with a blindfold on without hooking up Techstream and investigating. It could literally be anything.

Thank you for the advice, but I am in fact investigating. I have provided the symptoms, and simply asking if anyone else has ever had height control by way of the ignition. Stated differently, if there’s any known correlation between the AHC switch and the ignition itself.

 

[Bisho]

The ignition powers the system, which is entirely electric (doesn’t need engine power). I believe if the sensors think the truck has settled from neutral it will raise the shocks appropriately. This is why I wonder if you have loose linkage that is moving around on you.

 

[David310]

I would check height sensors and suspension to make sure everything is tight. I would then hook up Techstream to view AHC values. Techstream is mandatory for anyone with AHC to dial in pressures and ride height so you will need it regardless. Post up AHC screenshot values here and we can help from there.

How-To: TechStream In 5 Minutes

Getting Techstream up and running can be a bit of a pain. Hopefully this helps someone get started quickly. Step 1: Purchase an OBD-II / Mini-VCI interface. - I have sold out of my cables and supply chains are back in order, so no reason to purchase more. Anything like this will work: Mini-VCI...

forum.ih8mud.com

 

[baltistyle]

As stated, check the links for the height sensors and make sure the nuts are tight. Make sure the link is lubed and not sticky. When I first got my LX, the rear sensor nut was loose, and the height was not consistent. That took just a few minutes to figure out how to do to send it back to stock height. And then you want to read the ABC link provided because it explains the logic of the system. To further understand you can look in the FSM..

An ahc switch is easily available and cheap on eBay.

In order for AHC to work, there is a computer that checks on the doors, and the brake pedal and the gear that you’re in, so this could entirely be the control module for the AHC system as well.

I personally would not suspect the switch, because the system is acting erratically, regardless of switch input.

Techstream is the way

 

[BW100]

The ignition powers the system, which is entirely electric (doesn’t need engine power). I believe if the sensors think the truck has settled from neutral it will raise the shocks appropriately. This is why I wonder if you have loose linkage that is moving around on you.

I’ll check the height sensors next and look to see if there’s any loose components. If I’m unsuccessful there, I’ll head down the Techstream rabbit hole.

 

[BW100]

As stated, check the links for the height sensors and make sure the nuts are tight. Make sure the link is lubed and not sticky. When I first got my LX, the rear sensor nut was loose, and the height was not consistent. That took just a few minutes to figure out how to do to send it back to stock height. And then you want to read the ABC link provided because it explains the logic of the system. To further understand you can look in the FSM..

An ahc switch is easily available and cheap on eBay.

In order for AHC to work, there is a computer that checks on the doors, and the brake pedal and the gear that you’re in, so this could entirely be the control module for the AHC system as well.

I personally would not suspect the switch, because the system is acting erratically, regardless of switch input.

Techstream is the way

Thanks for those tips. I’ll check each of those sensors for any looseness. I’m also wondering about the speed sensors at the front wheels. As someone mentioned, on my particular LX, speed does not lower the height as it was originally designed to do. Having said that, I think the truck believes that it is constantly in “N” height, as that’s what the dash display shows - even when the suspension is maxed out in height.

With so many suggestions to run Techstream, I guess that’s my next step. From what I gather so far, I’ll need an old obsolete Windows laptop, a mini VCI cable, and a software CD. I started with the “Techstream in 5 minutes” link above, which is now 64 pages long. The links provided for cables are no longer available, as those were from 2018. If anyone knows what particular version of VCI cable is adequate for a 2006 LX470, that would help immensely.

 

[Rhetoric]

Thank you for the advice, but I am in fact investigating. I have provided the symptoms, and simply asking if anyone else has ever had height control by way of the ignition. Stated differently, if there’s any known correlation between the AHC switch and the ignition itself.

You are most welcome. Your prior posts were insinuating you were seeking a magic solve-all bullet by listing your symptoms.

As a data point for you: When my truck is keyed on and not running, it never adjusts height on its own. It also will not adjust if I change the height with the button. The light on the dash will flash, but the pump does not run. The engine needs to be running, doors closed.

Techstream will show you the height sensor data you need. Checking physical linkages is also great advice.

The height control switches are known to get crumby as beverages get spilled on them. Mine still made adjustments, but the circuit for the backlighting was destroyed so I ended up replacing with a known good switch.

 

[BW100]

You are most welcome. Your prior posts were insinuating you were seeking a magic solve-all bullet by listing your symptoms.

As a data point for you: When my truck is keyed on and not running, it never adjusts height on its own. It also will not adjust if I change the height with the button. The light on the dash will flash, but the pump does not run. The engine needs to be running, doors closed.

Techstream will show you the height sensor data you need. Checking physical linkages is also great advice.

The height control switches are known to get crumby as beverages get spilled on them. Mine still made adjustments, but the circuit for the backlighting was destroyed so I ended up replacing with a known good switch.

Thank you for that info. I apologize if my previous posts came across that way; I was simply trying to list all of the symptoms to see if anyone else had ever experienced something similar. It still seems that no one has - which is strange, but suggests this is in fact a one-off, unique issue.

Similar to yours, except while running, and the doors closed: the H and L lights on the dash will flash when I toggle the switch, but the pump does not run, and the height does not change. The only height changes occur with ignition ON, or running. Perhaps it’s worth noting, maybe not, but regardless: turning the key to ON, truck lowers .5”…this can occur with the drivers door open OR closed. Doesn’t matter. But for it to lift .5” with the truck running, the drivers door must be closed.

I’ll try a known working switch first, and then I’ll move in the direction of Techstream. I’m just way behind the curve when it comes to Techstream, but I can easily gather from the replies so far that many people are using it. It’s one of those things that would have been great to already have and be familiar with, rather than acquiring it and learning it on the fly.

Thanks again for the help.

 

[LJE]

Thank you for that info. I apologize if my previous posts came across that way; I was simply trying to list all of the symptoms to see if anyone else had ever experienced something similar. It still seems that no one has - which is strange, but suggests this is in fact a one-off, unique issue.

Similar to yours, except while running, and the doors closed: the H and L lights on the dash will flash when I toggle the switch, but the pump does not run, and the height does not change. The only height changes occur with ignition ON, or running. Perhaps it’s worth noting, maybe not, but regardless: turning the key to ON, truck lowers .5”…this can occur with the drivers door open OR closed. Doesn’t matter. But for it to lift .5” with the truck running, the drivers door must be closed.

I’ll try a known working switch first, and then I’ll move in the direction of Techstream. I’m just way behind the curve when it comes to Techstream, but I can easily gather from the replies so far that many people are using it. It’s one of those things that would have been great to already have and be familiar with, rather than acquiring it and learning it on the fly.

Thanks again for the help.

You're not anywhere near south-central Indiana, are you? I'd be more than happy to lend a hand if you're close.

Techstream really isn't bad once you get rolling - this is the exact cable I got & use with the VM in the "Techstream in 5 minutes" thread: https://www.amazon.com/dp/B07JYSPBGT?ref=ppx_pop_mob_ap_share

 

[BW100]

You're not anywhere near south-central Indiana, are you? I'd be more than happy to lend a hand if you're close.

Techstream really isn't bad once you get rolling - this is the exact cable I got & use with the VM in the "Techstream in 5 minutes" thread: https://www.amazon.com/dp/B07JYSPBGT?ref=ppx_pop_mob_ap_share

I would take you up on the offer, but unfortunately I’m nowhere near you. I’m in south Alabama.
Thank you for the link to that cable. I’ll get one on the way.

 

[94SRUNNER]

Techstream is the go-to for the do-it-yourself 100 Series owner.

You could try cross-posting your search for Techstream help in either or both of the Alabama Clubhouse forums...

AL- DixieLand Cruisers

forum.ih8mud.com

AL- Hot South Cruisers

forum.ih8mud.com

If those dont work...there are several surounding LC groups.

North American Clubhouses - East Region

East of the Mississippi River

forum.ih8mud.com