C0712

DTC C0712

DTC Descriptors

DTC C0712 01

Level Control Compressor Relay Circuit Short to Voltage.

DTC C0712 06

Level Control Compressor Relay Circuit Short to Ground or Open.

Diagnostic Fault Information

Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview

Circuit/System Description

The Automatic Level Control (ALC) system uses a compressor relay to switch 12 volts to the compressor motor. The electronic suspension control module (ESCM) receives inputs from the suspension position sensors and air pressure sensor to determine when to raise the rear of the vehicle by grounding the relay coil circuit, and monitoring to ensure it agrees with the command.

Conditions for Running the DTC

C0712 01
^ The ignition is ON.
^ The relay is commanded ON.

C0712 06
^ The ignition is ON.
^ The relay is commanded OFF.

Conditions for Setting the DTC

C0712 01

Upon detection of the compressor relay control circuit is shorted to battery.

C0712 06

Upon detection of the compressor relay control circuit shorted to ground, or open.

Action Taken When the DTC Sets

C0712 01 06

^ DTC C0712 is stored in memory.
^ The driver information center (DIC) displays the SERVICE SUSPENSION SYSTEM message after detection for 3 consecutive ignition ON cycles.
^ The ALC system is disabled.

Conditions for Clearing the DTC

^ A current DTC will clear when the malfunction is no longer present.
^ The history DTC will clear after 100 fault-free ignition cycles.

Reference Information

Schematic Reference

Automatic Level Control Schematics

Connector End View Reference

Automatic Level Control Connector End Views

Description and Operation

Automatic Level Control Description and Operation

Electrical Information Reference

^ Circuit Testing
^ Connector Repairs
^ Testing for Intermittent Conditions and Poor Connections
^ Wiring Repairs

Scan Tool Reference

^ Scan Tool Data List
^ Scan Tool Data Definitions
^ Scan Tool Output Controls

Circuit/System Verification

Ignition ON, command the compressor relay ON and OFF with a scan tool. Listen for the compressor running or relay clicks.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the compressor relay.
2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 86 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 ignition circuit terminal 85 and ground.
^ If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition circuit fuse is open, test or replace the compressor relay.

4. Verify that a test lamp illuminates between the ignition circuit terminal 30 and ground.
^ If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition circuit fuse is open, test the control circuit at terminal 87 for a short to ground.

5. Disconnect the harness connector at the air compressor.
6. Test for less than 1 ohm of resistance between the air compressor ground circuit terminal G and ground.
^ If greater than 1 ohm, test the ground circuit for an open/high resistance.

7. Connect the harness connector at the air compressor.
8. Connect a 40-A used jumper wire between the ignition circuit terminal 30 and the control circuit terminal 87. Verify the air compressor is activated.
^ If the air compressor does not activate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the air compressor.

9. Connect a test lamp between the ignition circuit terminal 85 and the control circuit terminal 86.
10. 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 ESC 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 ESC module.

11. If all circuits test normal, test or replace the compressor relay.

Repair Instructions

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

^ Air Compressor Replacement
^ Control Module References for ESCM replacement, setup, and programming