C0657

Circuit Description
The compressor is switched ON and OFF via an Automatic Level Control compressor relay which is controlled by the Electronic Suspension Control Module. The control module circuitry provides a switched path to ground whenever compressor activity is required. This circuit 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 using the scan tool.

Conditions for Setting the DTC
The DTC is set when the Electronic Suspension Control Module sees a low voltage condition at the Compressor Control circuit during a compressor OFF state.

Action Taken When the DTC Sets
The ELC compressor relay output drive is disabled for the remainder of the ignition cycle.

Conditions for Clearing the MIL/DTC
^ The scan tool can be used to clear the DTC.
^ The On-Board diagnostics 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 low voltage in the Compressor Control circuit while the ELC compressor relay output drive is in an OFF 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 ELC compressor relay output is commanded to the OFF state, which occurs whenever compressor activity is not required. The control module expects to see a high voltage condition during the OFF state.
Only electrical problems with the ELC compressor relay coil circuit are flagged. Compressor motor problems and air leakage problems do not set a DTC, but the Electronic Suspension Control Module shuts the ALC compressor relay off if there is no progress, or if excessive run times occur. Recovery is not attempted until the ignition is cycled OFF and ON.

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






DTC C0657 Level Control Compressor Circuit Low