GMC Troubleshooting Questions? Ask a Mechanic for Answers
Hello, I saw your question going unanswered and I wanted to assist you here. I've fixed a similar problem on a Cadillac Escallade, These systems tend to be similar, I wanted to see if I could help you here. Is your Denali giving you a "SERVICE RIDE CONTROL" or "SERVICE AIR RIDE" on the DIC display in the instrument cluster? If so you will need to use a certain type of scantool that will communicate with this ESC module to see what codes are active or stored in the module. The module closes the ground for the ALC relay circuit to power the compressor. If you can post the codes here , I can continue to assist you here. Thank you,
Ok got it , thank you for the details. take a look at the wiring diagrams I have posted here, If you can post the diagrams you have I'll compare the two. Here's what I got for an 04 Escallade ESV. If I cant help you here I'll re-submit your question so hopefully a GMC Tech can further assist you. I Just want to make sure you get taken care of first and foremost!
I got it , thank you. Have you tested resistance from the other side of the plugs from the level sensors. not the harness to the module , but the sensors themselves? I just wonder if they are open or shorted, 0.2 ohms would be shorted and OFL would be electrically open as I'm sure you already understand. Also, if you have the electrical pin breakdown for the compressor would help. If the exhaust solenoid fails , it shuts down the compressor as well. However manually closing the switch closes the ground to power up the compressor. You are pretty much doing what the module should be doing but it cant because its not getting the correct inputs from either the steering sensors (if applicable ), level sensors, exhaust solenoid ect. I"d like to see what codes are present , The SRS codes may also interfere with this operation. I would start ohm testig the level sensors and any component possible related to the compressor for opens or shorts, then if still inconclusive , scan all the codes present on the truck to see what the module is seeing and that should guide you in the right direction.
That sounds like a plan, next chance you get , with all the connectors plugged together , back probe points H and D you should get 12volts. and with the key in the run position, points G and D you should get 12 volts. By the way, you don't happen to be in any freezing weather conditions? Freezing temps seem to lock the compressors up. Usually below (25deg). Let me know how it goes, ill check back tomorrow. Best of luck!