I’ve been ignoring the “service suspension system” light on this thing long enough. I’ve already replaced the compressor and both rear shocks. The front struts I ordered are still on backorder and they can’t give me an estimated ship date so I went ahead and ordered some conversion struts with resistors just to get new struts on there and I’ll swap them out when the magneride struts become available.
The system does its self diagnosis on startup and you can hear the compressor run but I still didn’t think the air ride was working like it should. Which makes sense because if that light is on due to a code being set, it most likely disables the system.
Recently a service air bag message came up and that’s what prompted this fishing expedition. I read the code for air bag and it was seat position sensor. That was an easy fix, she must have shoved something under the seat and snagged the wiring and pulled the plug out of sensor. It broke the locking tab off but I just put a dab of super glue on it and it’s tight and light is off.
So while I’m scanning I decided to dig into the suspension system. All my level sensors are working properly, but I’m seeing the air pressure is reading 189PSI. That can’t be right. So I command the exhaust valve to open and pressure doesn’t change. I turn on compressor and pressure doesn’t change. Maybe it’s a bad pressure sensor?
I get under the truck and unplug the main connector to the compressor thinking, let’s start at the basics. KISS method. Connector looks good, terminals aren’t corroded or dirty. Unplug the pressure sensor and same thing, connector and terminals looks good. So I test continuity between main plug to sensor plug and all three wires passed. There’s a 5V reference wire that is gray on vehicle side of main connector and is red on compressor side to the sensor. I test for voltage and I’m seeing 4.86V. That’s good. Then there is a low reference wire that is brown on vehicle side connector, yellow on compressor side. And the sensor signal wire that is tan on vehicle side, green on compressor side.
To test the low reference side I pulled the ESC/ALC 30A fuse from underhood fuse box and then checked resistance with pressure sensor disconnected on that yellow wire going back to control module and ground. Spec is less than 2 ohms and I read 1.6ohms. So now I need to test my reference wire going back to control module. I just wanna make sure I don’t have a break in the wire.
In order to do this I need to drop the spare tire because the module is above the spare. That damn safety latch BS is fighting me again! I’m not having this thing do this to me if I ever need to change a tire on side of road. So I used a ratchet strap and secured tire up and lowered the cable. Got up there with a screw driver and release the safety latch. Dropped the spare tire and completely removed the tire cable assembly. That thing was a rust bomb so I threw it in the sandblast cabinet and knocked all the rust off it.
I noticed the spring on the end is broke in 2 spots. Ask me if I care! It’s getting spray bombed and soaked in oil and antisieze and going back on.
With that out of the way, I pulled the module down and disconnected the connector. Tested the wires going to compressor.
Compressor plug. Module connector
Pin H Gray wire-5V supply Pin6
Pin C White wire- air exh Pin8
Pin F Brown wire- low ref Pin12
Pin A Tan wire- sensor sig Pin34
I tested the air exhaust wire too just to make sure and it was good. All my power and grounds are good also. So there’s only one thing it can be, a bad automatic suspension control module.
Now I bought a used one a long while back thinking I could just program it for this vehicle and it’ll be good to go. Not the case. The number on module cross references ending in 07 model year. Completely different controller.
This is the one from mine.
So that sucks. I can get one that’s 6 weeks out at the low cost of $600. The part number supersedes to a 25971217 which I found for $438. I’ll still have to program it which will only cost me $40 licensing fee through GM’s website for the Tech2. So hopefully that solves my issue and this thing will ride like factory again. Once the magneride struts decide to show up. I don’t even think she appreciates the time, money and effort I put into this truck.