Service ride control

Hello,

9 times out of 10 it is the because the rear shocks are leaking here is instructions and diagrams so you can fix the problem you can get the parts on Amazon for $245.00 AC Delco

https://www.amazon.com/gp/product/B001KSC6LM/ref=as_li_qf_asin_il_tl?ie=UTF8&tag=2carprcom-20&creative=9325&linkCode=as2&creativeASIN=B001KSC6LM&linkId=49127f7bdf3bbf8cb6192cdb13846773

Check out the diagrams (Below). Please let us know if you need anything else to get the problem fixed.

When you start the vehicle, or apply some load to the rear, do you hear the compressor activate to level the vehicle. Most cases involve an inoperative level ride due to either a faulty compressor, or circuit faults that create an inoperative compressor. If the compressor is faulty, look for a condition that may have contributed to it, like split shock bladders or lines. If an exhaust solenoid fault is detected, it is integral to the compressor. Aside from hearing the compressor operate, you can also investigate and check the shocks for some pressure in the bladders, it should have some.

C0660 is an exhaust solenoid fault relevant to the automatic level control. It can be wiring, or a failed solenoid, which is part of the ALC compressor. To diagnose it, you would more than likely need a scan tool, a wiring schematic, and a meter.

You need a scan tool that will access the ALC system. I don't know if aftermarket scanners will accomplish that task. If your mechanics scanner has that capability, he should be more than capable. By accessing, I mean more than just reading codes. It would need to perform special functions like outputs, and have the ability to read data. Simply stated, if you can energize the relay circuit, and verify it at the compressor, then it needs a compressor.