I recently picked up a new to me 2002 LX470 at a very good price knowing that the AHC was non-functional. I have experience with the system, including using techstream to diagnose issues, but this one has me stumped.
Symptoms: The vehicle is at approximately the correct ride height, but quite stiff. No codes. Pressing either the up or down switch causes the green light to blink, but nothing happens. The light will blink forever until using the switch to move it back to N. No motor noise, no solenoid noise, nothing. All doors shut, confirmed with techstream. Comfort dial has no effect on ride.
Diagnostic work so far: Jumped the AHC motor directly, it seems to work. B+ and IG show 12V+. Used the techstream to perform active test on the relays, leveling solenoids, gate solenoids, etc. Nothing happens. No clicks, no noise, no movement. I performed the signal test, all signals are recognized by the ECU (steering, doors, low range, CDL, etc). Performed active test again using the jumper method, same result as before (no movement, no noises, nothing).
I unplugged the harness to the control valve and immediately had codes. That tells me the ECU isn't totally dead. It seems to receive signals just fine, but isn't outputting anything. I have also checked the main relay and the AHC relay, and associated fuses. The main relay is powered and works. The AHC relay tests fine, but never receives any signal to activate.
Height sensors also check out fine, I have tested them throughout their range and have found no dead spots (using the techstream)
Pressure sensors read zero (accumulator, and all 4 corners). I can't go through the proper process (low to N) to check them.
I'm fairly stumped, and thinking about pulling the trigger on a used AHC computer.
Symptoms: The vehicle is at approximately the correct ride height, but quite stiff. No codes. Pressing either the up or down switch causes the green light to blink, but nothing happens. The light will blink forever until using the switch to move it back to N. No motor noise, no solenoid noise, nothing. All doors shut, confirmed with techstream. Comfort dial has no effect on ride.
Diagnostic work so far: Jumped the AHC motor directly, it seems to work. B+ and IG show 12V+. Used the techstream to perform active test on the relays, leveling solenoids, gate solenoids, etc. Nothing happens. No clicks, no noise, no movement. I performed the signal test, all signals are recognized by the ECU (steering, doors, low range, CDL, etc). Performed active test again using the jumper method, same result as before (no movement, no noises, nothing).
I unplugged the harness to the control valve and immediately had codes. That tells me the ECU isn't totally dead. It seems to receive signals just fine, but isn't outputting anything. I have also checked the main relay and the AHC relay, and associated fuses. The main relay is powered and works. The AHC relay tests fine, but never receives any signal to activate.
Height sensors also check out fine, I have tested them throughout their range and have found no dead spots (using the techstream)
Pressure sensors read zero (accumulator, and all 4 corners). I can't go through the proper process (low to N) to check them.
I'm fairly stumped, and thinking about pulling the trigger on a used AHC computer.