• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
• | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
• | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
---|---|---|---|---|
Automatic Level Control Relay Coil B+ | C0712 06 | C0712 06 | -- | -- |
Automatic Level Control Relay Coil Control | C0712 06 | C0712 06 | C0712 01 | -- |
The electronic suspension control module (ESCM) adjusts the vehicle suspension ride height. The ESCM determines the height of the vehicle based on the voltage from the suspension position sensors. The module grounds the ELC relay and the exhaust control solenoid to raise and lower the vehicle in order to keep the vehicle level.
• | The ESCM is powered up. |
• | The ESCM is commanding the compressor ON. |
The compressor relay control circuit is shorted to voltage, ground, or open for 5 seconds.
The automatic level control (ALC) system will be inoperative.
The ESCM does not detect a failure during the self test.
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 ESCM retries the output every 15 seconds to try to recover from the fault.
Automatic Level Control Schematics
Automatic Level Control Description and Operation
Control Module References for scan tool information
Ignition ON, command the compressor relay ON with a scan tool. Listen for the operation of the ELC relay and the automatic level control compressor.
Important: Whenever repairing and/or replacing ALC system components, perform the Suspension Position Calibration procedure.
⇒ | If the test lamp illuminates, test the control circuit for a short to voltage. |
⇒ | 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 B+ circuit fuse is open, test the control circuit terminal R8 for a short to ground or faulty ALC compressor motor. If all circuits test normal, test or replace the ELC relay. |
⇒ | If the test lamp does not illuminate, test the B+ circuit for an open/high resistance. |
⇒ | If greater than 1 ohm, test the ground circuit for an open/high resistance. |
⇒ | If the ALC compressor does not activate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the ALC compressor. |
⇒ | If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the electronic 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 electronic suspension control module. |
⇒ | If the resistance is not within the specified range, replace the relay. |
• | 30 and 86 |
• | 30 and 87 |
• | 30 and 85 |
• | 85 and 87 |
⇒ | If not the specified value, replace the relay. |
⇒ | If greater than the specified range, replace the relay. |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
• | Control Module References for ESC module replacement, setup, and programming |