2005 LX470 AHC Issues - New Owner (1 Viewer)

[OregonB]

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.

View attachment 2325280


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.

View attachment 2325281

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.

wonderful write. Hope never to need, but now I know. thanks.

 

[LndXrsr]

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).

Any thoughts?

Agree your issue is with sensor height discrepancies. The FL sensor may be correct if the AHC has dropped to "Low" or further down near the bump stops. Minus values indicate heights below neutral. The FR sensor still seems like maybe something isn't right.

Where are your sensors positioned in their brackets? You could try swapping just the sensors themselves left to right and see what readings you get.

 

[HMLX470]

Long overdue update, but good news!

So I swapped the sensors from left to right to no avail. I thought maybe it was the Suspension computer itself, but I decided to replace the whole sensor arms first. I was able to find a deal on Amazon for both front ones for ~$200. I had to borrow a heavy duty jack and jack stands from a buddy since my front was completely lowered from the error.

2.5 hours later, I was pleased to see the suspension work. I had to change both sides for it to fully start working, and after almost 1.5 months of owning it, I was able to cycle through the cycle through the height modes!

Thanks to everyone for your help! Next steps are to start doing general maintenance items including the timing belt (if needed) to bring this back to optimal operating condition. If I find a deal on some 33" wheels/tire combo, I might grab them as well.