C0663

Circuit Description
The Automatic Level Control (ALC) exhaust solenoid valve is controlled (switched ON or OFF) by the Electronic Suspension Control Module. The control module provides a low-side drive (switched to ground) whenever exhaust activity is required and during a head-relief sequence. The head-relief sequence occurs at compressor start-up. This drive output from the Electronic Suspension Control Module is also continually monitored to determine if the voltage level agrees with the commanded state.

Conditions for Running the DTC
^ The ignition is on.
^ The fault is detected during three consecutive ignition cycles, or during the same ignition cycle after clearing the DTC with the scan tool.

Conditions for Setting the DTC
The DTC is set when the Electronic Suspension Control Module measures a feedback voltage in the exhaust solenoid control circuit greater than a preset value during an exhaust solenoid valve ON-state.

Action Taken When the DTC Sets
^ All rear leveling activity for the remainder of the ignition cycle will be disabled.
^ The SERVICE RIDE CONTROL message will be displayed.

Conditions for Clearing the MIL/DTC
^ The scan tool can be used to clear the DTC.
^ The On-Board diagnostic CLEAR RSS CODES feature can be used to clear the DTC.
^ The DTC is saved as history when the Electronic Suspension Control Module no longer sees a high voltage in the exhaust solenoid control circuit when the exhaust solenoid valve is in an ON-state. The DTC will clear if the fault does not return after 50 consecutive ignition cycles.

Diagnostic Aids
This fault condition is detectable only when the exhaust solenoid valve output is commanded to the ON-state, which occurs before each compressor start-up and whenever a downward correction is necessary. The Electronic Suspension Control Module expects to see a low voltage condition during the ON-state.
Only electrical problems with the exhaust solenoid valve are flagged. Air blockage problems do not set a DTC, but the Electronic Suspension control Module shuts off the exhaust function if no progress is made or if excessive run time occurs.

Test Description
The number(s) below refer to the step number(s) on the diagnostic table.
2. Listen for an audible click when the solenoid operates. Command both the ON and OFF states. Repeat the commands as necessary.
3. Tests for voltage at the coil side of the solenoid. The ELC fuse supplies power to the coil side of the solenoid.
4. Verifies that the Electronic Suspension Control Module is providing ground to the solenoid.
5. Tests if ground is constantly being applied to the solenoid.