Automatic Level Control

DTC C0712 (Symptom 01)

DTC Descriptor

DTC C0712 01

Level Control Compressor Circuit High

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) adjusts the vehicle suspension ride height. The electronic suspension control (ESC) module determines the height of the vehicle based on the voltage from the ALC sensor. The ESC 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 ESC module is powered up.
* The ESC module is commanding the compressor ON.

Conditions for Setting the DTC

The compressor relay output is shorted to battery for 10 seconds.

Action Taken When the DTC Sets

The ALC will be inoperative.

Conditions for Clearing the DTC

The ESC module 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 ESC module retries the output every 15 seconds to try to recover form the fault.

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 ALC compressor.

Circuit/System Testing

1. Ignition OFF, disconnect the ELC CMPRSR relay.
2. Ignition ON, verify that a test lamp does not illuminate between the 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 B+ circuit terminal 15 and ground.
^ If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ELC CMPRSR fuse is open, test the control circuit terminal 12 for a short to ground. If the circuit tests normal, test or replace the ELC CMPRSR relay.

4. Connect a test lamp between the B+ circuit terminal 15 and the control circuit terminal 11.
5. Command the ELC CMPRSR 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.

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

Component Testing

Relay Test

1. Ignition OFF, disconnect the ELC CMPRSR relay.
2. Test for 40-200 ohms of resistance between terminals 85 and 86.
^ If the resistance is not within the specified range, replace the relay.

3. Test for infinite resistance between the following terminals:
^ 30 and 86
^ 30 and 87
^ 30 and 85
^ 85 and 87

^ If not the specified value, replace the relay.

4. Test for less than 2 ohms of resistance between terminals 30 and 87A.
^ If greater than the specified range, replace the relay.

5. Install a 3-amp fused jumper wire between relay terminal 85 and 12 volts. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 ohms of resistance between terminals 30 and 87.
^ If greater than the specified range, replace the relay.

Repair Instructions

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

* Relay Replacement (Attached to Wire Harness) Relay Replacement (Within an Electrical Center)
* Control Module References for Electronic Suspension Control Module replacement, setup and programming.