2005 LX470 AHC Issues - New Owner (2 Viewers)

[HMLX470]

Hi Everyone - I finally pulled the plug and bought an 05 LX470 over the weekend. I have been looking at these for a while, and ended up finding one I couldn't pass up.

The truck was in good shape overall and had minor rust as expected from a Northerner truck ( I live in PA). The main issues were that it needs a new windshield and the dreaded AHC system. I didn't mind the AHC system problem as I am hoping to one day put a lift kit on it, but want to make it rectify the issue for the moment while I decide.

Windshield: The windshield I know needs to be replaced properly with Toyota sourced rivets and I have a shop looking into that at the moment.

AHC: The major pain point is the AHC system. Currently, the front is at "HI" position, while I believe the rear is at "N". The truck is not responding at all to the switch and the green leds blink until they stop, but the truck does not lower or raise either the front or rear. I checked the reservoir and that has fluid at the max level. I am waiting on my mechanic to get onto a lift, but I wanted to post here as well to see if anyone else had the same issues and could shed some light.

After researching on the forum, I believe the globe accumulators should be replaced along with a Fluid flush.

Thoughts?

Pics: 2005 LX470 with 159K miles

 

[uHu]

The ahc problem is most likely a faulty height sensor, or cable/plug; a minor problem. You don't know if there is any point in changing the globes until you have the heights and pressures under control, and then check the globes. Do some reading on the link below. And why would you change to a permanent lift when you already have a 2" lift at the push of a button?

Definitive list of AHC maintenance items

My nagging "issue" with AHC is wondering if the suspension doesn't feel quite right. I feel bumps pretty well and I subjectively recall an older 100 series land cruiser standard suspension feeling like being on a cloud vs the small cracks in the road. The question is driving me insane when I'm...

forum.ih8mud.com

 

[suprarx7nut]

Hi Everyone - I finally pulled the plug and bought an 05 LX470 over the weekend. I have been looking at these for a while, and ended up finding one I couldn't pass up.

The truck was in good shape overall and had minor rust as expected from a Northerner truck ( I live in PA). The main issues were that it needs a new windshield and the dreaded AHC system. I didn't mind the AHC system problem as I am hoping to one day put a lift kit on it, but want to make it rectify the issue for the moment while I decide.

Windshield: The windshield I know needs to be replaced properly with Toyota sourced rivets and I have a shop looking into that at the moment.

AHC: The major pain point is the AHC system. Currently, the front is at "HI" position, while I believe the rear is at "N". The truck is not responding at all to the switch and the green leds blink until they stop, but the truck does not lower or raise either the front or rear. I checked the reservoir and that has fluid at the max level. I am waiting on my mechanic to get onto a lift, but I wanted to post here as well to see if anyone else had the same issues and could shed some light.

After researching on the forum, I believe the globe accumulators should be replaced along with a Fluid flush.

Thoughts?

Pics: 2005 LX470 with 159K miles

Welcome!

For AHC, sounds like a valve is seized closed up front or something. You should be able to bleed some of that fluid out to get the front down. I think you'll need someone familiar with AHC (and techstream) to be helpful troubleshooting. I can already foresee 9/10 mechanics saying immediately "rip out that darn system, it never works right anyways." Don't listen to those mechanics.

I bet the fix is very simple if you can find the right mechanic that knows how the system works.

Unless the system is rusted badly, IMO, a lift kit is a big step backwards. Figure out what's going on with AHC first.

 

[jahawk]

This has worked for me before, and it's a free place to start.

"manual clear: ignition off, short Tc and E1 in dlc1, ignition on and push brake pedal 9 times in less than 3 seconds. IG off, remove short. "

 

[HMLX470]

Thanks for the quick responses guys. The reason I have the lift kit as a back up plan is that I don't want to sink too much money into AHC as I am not fully sure of the issue.

Anyone have a Northeast shop they recommend? I am in the Allentown, PA area.

@jahawk Can you explain this a bit more?
""manual clear: ignition off, short Tc and E1 in dlc1, ignition on and push brake pedal 9 times in less than 3 seconds. IG off, remove short. "

 

[suprarx7nut]

Thanks for the quick responses guys. The reason I have the lift kit as a back up plan is that I don't want to sink too much money into AHC as I am not fully sure of the issue.

Anyone have a Northeast shop they recommend? I am in the Allentown, PA area.

@jahawk Can you explain this a bit more?
""manual clear: ignition off, short Tc and E1 in dlc1, ignition on and push brake pedal 9 times in less than 3 seconds. IG off, remove short. "

If the financial aspect is a part of the equation, take the time to write out the costs involved with a lift purchase and AHC delete. It's uncommon for AHC repairs to exceed the price of a typical static lift kit. If you just want to throw in some used non-AHC suspension parts you can save a lot. If you want a 2+" lift kit you're probably going to spend more on the static lift than you will on most the common AHC fixes.

 

[ramangain]

When you try to operate the AHC system, is the pump running below the resevoir? Simple things; check that the plug is in and secure. Then check the connector going to the pump with a multimeter to ensure it gets power when it should. AHC gurus should chime in as to which pins to check.

 

[jahawk]

On the passenger side fender well you'll find this diagnostic port. Jump Tc and E1 then do the process described, It clears all AHC codes.

 

[HMLX470]

I will check the pump to see if I hear it activate. @jahawk - What kind of wire is that? I am have never seen anybody short a car like that.

 

[Biga27110]

I will check the pump to see if I hear it activate. @jahawk - What kind of wire is that? I am have never seen anybody short a car like that.

If you need any parts PM me ive switched over to OME and all my AHC parts are available.

 

[jahawk]

That's a tool to remove a radio face that I had lying around. I keep it in my tool kit. A paper clip works just as well.

 

[LndXrsr]

That front end is HIGH. Nice reverse-rake, interesting style choice by the PO.

I think Techstream is going to be your friend here to see if you can pinpoint a sensor or other error code. You can find a shop or nearby Toyota fan that has one, or get your own:

- Start here for info on the software and loading it onto pretty much any computer: Techstream in 5 minutes.
- Get a Mini-VCI cable from Amazon or eBay that claims to work with Techstream. Many are sketchy, but most are worth the $20-30 chance. Once you get it communicating with your truck, Techstream can read AHC error codes, measure sensor heights, and measure AHC pressures which are key for a good ride.

 

[Trackmail]

I just did this dance on my 04 LX470. Exact same symptoms. Diagnosis was way longer then the fix. Lots of treads have you start with codes and bleeding and worrying about bad globe$.

15 year old NE car, you likely have a bad front height sensor. I just replaced mine, (sensor only, $19 Amazon). I will update post with disassembly, testing, pictures and part numbers in a day. Hang in there.

 

[VirginiaSlim]

I have an ‘04 LX and my rear AHC went bad—rear was riding way low and provided no shock dampening. Instead of going through the rather tedious AHC diagnosis, getting techstream, etc., I put in traditional old man emu springs and fox shocks. In a perfect world for how I use the truck, I’d probably take the AHC because it rode smoothly and was nice to help people get in and out, get under low parking structures, etc. But at the end of the day my truck had enough rust that I figured I’d be replacing AHC components regularly enough that I didn’t want to mess with it. You could try making a couple of the easy cheap fixes mentioned here or on the other threads first to see if that solves it. Good luck.

 

[Trackmail]

As promised: $19 AHC fix.

2004 LX470 184,000. Automatic Height Control (AHC) System not working.
I started by pulling and checking fuses and codes (learned that a bad sensor doesn’t have a code but here is my workflo. I suggest the OP skip this part based on his symptoms:
#3: 50amp (engine bay)
#34: 15amp (drivers kick panel)
#37: 20amp (drivers kick panel)
Visual inspection: Height sensors, wires, plugs all seemed fine.
Jumped system into manual mode and reset all codes, no change.
Logged in with Foxtool NT530 with Toyota/Lexus diagnostician software. Techstream or a Techstream knockoff is GREAT investment if you have one of these trucks and if you are a Toyota/Lexus family you will get lots of uses from it. I have five different brands in my fleet so I picked the NT530 because I can load software for each of them into one tool, interface isn’t as slick as Techstream so if I was Toyota’s only would use TS.
Running in Active Test mode I tested AHC pump motor and relays everything was fine.

OP start here: Removed driver’s side height control sensor and arm. No need to jack up car, because your car is stuck in front HI it is easy to reach around/over wheel to access. Sensor removal:

1. SOAK bolt at end of sensor arm to suspension pick up point in PB Blaster.
2. 2x14MM bolts to frame, loosen both until just holding bracket on.
3. Remove 10MM bolt at end of sensor arm link to suspension mount, 10MM opened end wrench on back of nut to keep from spinning (make a mark or take a picture of where the suspension link is within its mounting slot). I choose to remove link from suspension pickup point because I didn’t know how much force was going to be involved so I didn’t want to stress the arm by separating at the arm to link joint. Next time I will separate at link to arm joint then I won’t have anything to mark Make sure you tap all the rust of the nut and you have great contact with the nut before you start turning. Once nut is off arm it will (should) move very freely
4. Cut cable tie that holds wiring harness to bracket, unclip sensor from wiring harness.
5. Holding sensor arm and sensor assembly with one hand to prevent from over extending arm, now finish removal two bolts to frame.

Pic of my passenger side post replacement.

I found this video showing the guts of a sensor:

Driver side: My driver side was a little dirty inside, cleaned up with contact cleaner and a q-tip. Tested with OHM Meter. Center pin on connector is ground. Tested each outside pin to ground, my outside pins ranged 550-1950 and 450 -1950 as you moved arm. During reasembly sensor cover screws should be snug but don’t overtighten at risk of cracking housing.

Passenger Side: Mine was completely fried inside, clearly had gotten wet or dirty enough to cause an arc vaporize everything.

Parts search: I only found full assemblies available based on the Lexus part numbers below. OEM assemblies are ⅓ to ½ of factory cost. All seemed more then I needed so I kept looking and found what appeared to be the sensor only but I could not get that part number to match for 2004. Sensor looked identical and for $19 with Amazon Prime free return I thought it worth a try.

Factory Parts:
Front AHC Height Sensor Left (driver): Lexus 89406-60012 SENSOR SUB-ASSY, HEIGHT CONTROL $399
Front AHC Height Sensor Right (pass): Lexus 89405-60012 SENSOR SUB-ASSY, HEIGHT CONTROL $399
AMAZON: can order sensor only without arms/fittings ($35-$45)

Rear AHC Height Sensor Rear: Lexus 89407-60010 SENSOR SUB-ASSY, HEIGHT CONTROL, REAR $445

SENSOR ONLY replacement AMAZON:: RAZ AUTO PARTS Suspension-Headlight Leveling Sensor for Lexus 2008-01, Mazda 2008-04, Toyota 2009-04 - 89405-48020 - FE03-51-21YD $19. This sensor appears to fit all three locations on truck FR/FL/Rear.

New sensor tested with same range as my old (good) driver's side.

WARNING: Do not twist spindle on new sensor before installing assembly arm, arm and bracket have stops on them to prevent over extension, sensor does not have this internal protection.

I also ordered an aftermarket kit (~$200) of both DR/Pass full arm assemblies in case the sensor didn’t work. Sensor worked so those are getting returned.

Desemble your old sensor from bracket and install new sensor paying attention to direction of arm. I made sure that the new sensor’s back cover screws were snug before reinstallation which is the reverse of above. MAKE SURE you get sensor arm link back in same spot on suspension pickup. Yes I sanded, primed, painted and clear coated my old bracket before reinstalling .

Bottom line ACH rocks and once you know how it works sensors testing/updating and reinstalling is quick and easy. Also maintenance of this system is easy if you get yourself the software discussed above and with the new and awesome post everyone should be able to keep AHC alive: The ABCs of AHC - How to Measure, Flush, and Adjust all in one place

Truck is perfect now, I will keep you posted how long my $19 sensor vs. $400 factory part works.

 

[HMLX470]

Hi @Trackmail - Thanks for the detailed write up!!

I had the shop replacing my windshield use their computer to check codes, and the pic below was the result. I think I have a bad Front right and bad Rear sensor that is causing this issue. I will be trying your method starting with the front sensor to see if it works.

 

[uHu]

Not sure the rear sensor is bad from that data set. The AHC will cancel operation when the 2 front sensors are disagreeing this much, so the rear can actually be just that ~ 1/2 inch low.
Also, for the front sensor, it could be the cable or a plug. Either the plug at the sensor or the plug atop the fender. You'll soon find out, I suppose.

 

[LndXrsr]

As uHu mentioned, the sensors being that far off will mess with things in a major way. AHC tries to make the sum of those values as close to zero as possible. Not sure any of your sensors are bad, possibly just majorly misaligned. That being said, one or both of the fronts could be bad, but unclear which one with both values being so far from zero. They may have some corrosion inside leading to bad readings.

May want to try some sensor adjustments first and if that doesn’t fix it, open up both sensors and look for damage. Then order a replacement for the bad one if needed.

 

[Trackmail]

HMLX470, your readings are almost exactly what mine were and it was just one front sensor. Sensor removal is simple hand tools and a few minutes to get out and open up to do a visual inspection (it took way longer to type up the proceedure then to remove and reinstall a sensor ) If everything looks good inside blow out any dust, clean the contacts with a q-tip and alcohol and put it back together per my write up and video reference.

Suggestion clean up any dust, dirt, mud etc on the outside of the sensor before you take off the backplate so that there is no risk of contaminating the seal when you put it back together.

Lastly I will be updating my procedures post to include notes on resetting the VSC computer to recognize the knew sensor parts.

Let us know how you do!

 

[HMLX470]

Quick Update:

I replaced the front right sensor per @Trackmail 's advice. The truck leveled off, but the height selector switch was still not working. When I parked it on a grass hill, I think the suspension auto adjusted and lowered the front of the truck to "Low". Since then, the truck has not raised it's front suspension. Front is stuck on Low and rear is at Neutral. I ordered Techstream and I got the following readings today. I think it's not leveling due to the large discrepancy between the left and right wheels(right is the one I replaced and the reading is wrong).

I also realized I am not getting any pressure readings. My AHC fluid tank is also filled to more than Max by a good amount (might be due to front sitting on low?).

Any thoughts?