WELJ31

Hello all We have been fighting this problem for over a year now. Its been to the dealership and a couple local "auto electrical" shops.
2012 Suburban LTZ 4x4 with RPO z55
Front Shocks are Arnott bypass struts
Rear are regular shocks (with 50watt6R) resistors
The compressor has been replaced 4 times now. 3 times due to Arnott telling us the exhaust valve was bad. This was back when we had the Arnott shocks on back (non bypass). Any way we have tried ever thing we think of. The system has never worked for us. At this point we would love for it all to work as it should but after a year we would settle for just getting the "service suspension" message to go off. We have tried ever method we could find and still have the massage.
We are using AutoEnginuity software. showing DTC C0660 This software does not give the 01 / 06 for short to battery or short to ground.
When testing fuse #2 and #54 my tester shows a short. We have diagnostic instructions however we just dont understand all of it.
https://f01.justanswer.com/Bluegoril...ahoe_c0660.pdf
Circuit/System Testing
1. Ignition OFF, disconnect the automatic level control (ALC) compressor exhaust solenoid.
2. Ignition ON, verify that a test lamp does not illuminate between the solenoid control circuit
terminal C at the connector and ground.
㱺 If the test lamp illuminates, test the control circuit for a short to voltage.
3. Verify that a test lamp illuminates between the B+ circuit terminal B and ground.
㱺 If the test lamp does not illuminate, test the B+ circuits for a short to ground or an open/high
resistance. If the circuit tests normal, test or replace the ALC compressor.
4. Connect a test lamp between the B+ circuit terminal B and the control circuit terminal C.
5. With a scan tool, clear all ALC DTCs.
6. Engine running, command the exhaust solenoid ON and OFF. The test lamp should turn ON and
OFF when changing between the commanded states.
㱺 If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests

Thanks for any help you can provide.

WELJ31

BTW Compressor will kick on if we jump it at the under hood relay.

repairman54

I would say it's the Arnott bypass ''hack'' screwing up the system since it's been doing it so long. I've got the auto leveling system and the electronic shocks front and rear in my Tahoe. I have had to replace both rear shocks and the compressor over 140k miles now but because of its complexity I left the stock system in to avoid issues. One rear shock had electronic issues, other one blew out the air bag on it and the big air leak killed the compressor. First shock bad electronics at 50k miles, second one at 130k miles. I only changed one shock at a time also due to cost. I looked into Arnot but stayed away and glad for it.
Do not trust internet sites for diagnostics. I use alldatadiy.com for factory manuals for my vehicles.
I have the autoenginuety in my laptop also.
I would use a electronic cleaner/lubricant in every connector at the shocks, sensors, modules, etc. to make sure connections are good. With the factory manual you can trace and check all the grounding points also.

WELJ31

short to ground or to power still working on it