2011 Denali Suspension

I have a 2011 Denali with the air suspension. Last year we had a rear shock fail. It wasn't a leak but rather a sensor or check valve failed. It wasn't a case where the compressor was running constantly though. I only knew about the issue because I had the Service Suspension message in the DIC. I ended up replacing both of them.

Fast forward a year and half or so and we were hitching up our camper and noticed that the compressor never kicked in to level out the truck and even with the weight distribution bars in place it is low in the back so it should be doing something. The camper isn't that heavy probably around 6000 lbs with a GVWR of 6750. The odd thing is there is no warning messages in the DIC about a suspension issue. In the past with my code reader when there was a detected fault I couldn't read it. I had to go to the local Chevy dealer where my cousin works as a tech so he could read it for me. I know that the compressor failure is fairly common in these trucks but in asking my cousin if it that would throw a Service Suspension message and he felt that it would. I checked the fuse and it is good. In thinking about it I am wondering if it is possible that the sensor that detects the rear being low might have an issue. That might explain why the rear end is low and the compressor isn't kicking in. Also why there isn't a warning message.

For those that had compressor failures, did it throw a message or is it like my symptoms where it thinks everything is fine but it isn't doing anything? Anyone know where the sensors are for this system? It seems to me that my father had a similar issue many years ago with the Autoride in his 03 Tahoe. It was a sensor on the front suspension somewhere if I remember. That was probably 10 years ago though and a different generation truck so the system might be completely different. I also don't really know when it stopped working. We don't tow much for trailers in the winter. It worked last fall though.

Thanks

Well I have it working again. I thought I would post the resolution in case it might help others out there in the future.

So I went through and tested the 3 fuses that I found references to for the suspension system and they all tested good. I then located the relay for the system and with the truck running I jumpered the socket to complete the circuit. This test should result in the compressor starting and even if the truck isn't calling for it (bad sensor) or the relay has failed. Still nothing. This pretty much told me that odds are the compressor is shot which shouldn't be all that shocking as they seem to fail. Rather than order a new OEM, people seem to have been having luck with the Dorman Compressor. I guess in the past you had to splice in wires and such but now it is just unplug the old and plug in the new.

The new compressor came in today and I ran the truck up on the hoist. It took maybe 10 minutes to swap out and fired up the truck. I couldn't tell if it kicked in but I pulled out of my shop, opened the lift gate and sat on the bumper with the truck running. Nothing. I went over to my John Deere and pulled 252lbs of suitcase weights off the back of the tractor putting it in the back of the truck and then sat on the bumper. The compressor kicked in and I could feel the truck lifting up. So it was a failed compressor.

Next task was to replace a burned out headlight. Since the come in pairs I did both. That project took a lot longer than changing the compressor even though I did the method of pulling the air box out and for the other side the battery tray and shifting the washer reservoir out of the way.

So we are back up and running for this weekend as we are heading out with the new camper. This trip will be with a full water tank as well because there are no hookups so we are running up to the max limit on the cargo capacity and hitch limits. I really wanted to get the load leveling compressor working before heading out. Should be good.

I think your in the wrong section bud.