Air Suspension

DTC C0712

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.

DTC Descriptor
DTC C0712 00
- Level Control Compressor Relay Circuit

Diagnostic Fault Information





Circuit/System Description

The air suspension control module (ASCM) adjusts the vehicle suspension ride height. The ASCM determines the height of the vehicle based on the voltage from the suspension position sensors. The module grounds the ELC COMP relay and the exhaust control solenoid to raise and lower the vehicle in order to keep the vehicle level.

Conditions for Running the DTC

* The ASCM is powered up.
* The ASCM is commanding the compressor ON.

Conditions for Setting the DTC

* The leveling compressor relay coil control circuit is shorted to voltage, ground, or open for 5 seconds.
* The leveling compressor relay coil B+ circuit is shorted to ground or open for 5 seconds.

Action Taken When the DTC Sets

The air suspension will be inoperative.

Conditions for Clearing the DTC

The ASCM does not detect a failure during the self test.

Diagnostic Aids

This circuit is monitored during every functional operation of the compressor relay output and every 3.3 milliseconds when output is active. If a compressor relay fault is detected, the ASCM retries the output every 15 seconds to try to recover from the fault.

Reference Information
Schematic Reference

Air Suspension Schematics (Air Suspension Schematics)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Air Suspension Description and Operation (Air Suspension Description and Operation)
Electrical Information Reference

* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing For Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)

Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information

Circuit/System Verification

Ignition ON, command the compressor relay ON with a scan tool. Listen for the operation of the ELC CMPRSR relay and the air suspension compressor.

Circuit/System Testing

1. Ignition OFF, remove the ELC CMPRSR relay.
2. Ignition ON, verify that a test lamp does not illuminate between the rear fuse block relay control circuit terminal 11 and ground.

• If the test lamp illuminates, test the control circuit for a short to voltage.

3. Verify that a test lamp illuminates between the rear fuse block B+ circuit terminal 15 and ground.

• If the test lamp does not illuminate, test the relay B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the air suspension control module.

4. Connect a test lamp between the B+ circuit terminal 15 and the control circuit terminal 11.
5. Command the compressor relay ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

• If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the air suspension control module.
• If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the air suspension control module.

6. If all circuits test normal, test or replace the ELC CMPRSR relay.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Relay Replacement (Attached to Wire Harness) (Relay Replacement (Attached to Wire Harness))Relay Replacement (Within an Electrical Center) (Relay Replacement (Within an Electrical Center))
* Suspension Position Calibration (Suspension Position Calibration)
* Control Module References (Programming and Relearning) for air suspension control module replacement, setup, and programming