I didn't exactly follow the FSM procedure but did my own detective work with the schematic information that it provided.
Here are the things I did:
- Jumper motor control pins of the relay receptacle. Motor ran and rose car. Good.
- Swap relays to test the relay. Used a known good relay in the ALC slot. Did not work.
- DVM relay coil pins when I expected the compressor to run. Saw like 0.3V at most and then 0V. Not good.
- Unplugged Electronic Suspension Control harness at module in trunk. Harness has two pins of note. Pin 6, shorted to ground, grounds the other pin at the relay coil wire in the fuse box. After starting the car, this DID run the motor.
- The other pin of interest, pin 20, does the same thing but with the exhaust solenoid on the compressor. This also worked.
The last two are very telling. What it means is the entire system after the ESC module seems to be working properly, including the fuses, relays and wiring, and the compressor, air lines and shocks. What it also means is the ESC module does not seem to be commanding the compressor to run when it is supposed to (after ignition run). So either there is some logic that I don't understand...which to try to fix that, I disconnected the battery cables and touched them together to potentially reset things. Or, the ESC module itself is somehow malfunctioning.
What I really need at this point is a good Tech 2 (or aftermarket equivalent). I can trigger the compressor and relay via the ESC, and at least determine if the ESC is able to do so. I would also need the Tech 2 if I replaced the ESC module, to do some kind of initialization programming (ride height stuff, and maybe VIN code, etc.).
I think one of those tools would be a good investment and there are some good options under $500. Right now I will probably put the car back together and just drive it, hoping something will wake up and start working. Probably unrealistic.
ESC module.