Circuit Description
The automatic level control compressor is switched ON and OFF using an electronic level control (ELC) compressor relay which is controlled by the electronic suspension control (ESC) module. The ESC module circuitry provides a switched path to ground whenever compressor activity is required. This drive circuit is also continually monitored to determine if the voltage level agrees with the commanded state.
DTC Descriptors
This diagnostic procedure supports the following DTCs:
| • | DTC C0657 Level Control Compressor Circuit Low |
| • | DTC C0658 Level Control Compressor Circuit High |
Conditions for Running the DTC
The ignition is ON.
Conditions for Setting the DTC
C0657
The following conditions must be present to set the DTC:
| • | The ESC module detects voltage less than a preset value in the compressor motor control circuit during a compressor OFF state test. |
| • | The fault is detected during three consecutive ignition cycles, or during the same ignition cycle after clearing the DTC with a scan tool. |
C0658
The following conditions must be present to set the DTC:
| • | The ESC module detects voltage greater than a preset value in the compressor motor control circuit during a compressor ON state test. |
| • | The fault is detected during 3 consecutive ignition cycles, or during the same ignition cycle after clearing the DTC with a scan tool. |
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 DTC is saved as history when the ESC module no longer sees an out of range voltage condition in the compressor motor control circuit. The DTC will clear if the fault does not return after 50 consecutive ignition cycles. |
Diagnostic Aids
These DTCs are set only by electrical problems with the ELC compressor relay coil circuit. Compressor motor problems and pneumatic leakage problems do not set these DTCs.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step tests for voltage in the automatic level control relay coil supply voltage circuit.
-
This step tests for a short to voltage in the automatic level control relay coil supply voltage circuit.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Automatic Level Control Schematics | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |
Does the test lamp illuminate? | Go to Step 3 | Go to Step 4 | |
Does the test lamp illuminate? | Go to Step 7 | Go to Step 6 | |
4 | Test the ALC relay coil supply voltage circuit for a short to ground or an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 10 | Go to Step 5 |
5 | Inspect for poor connections at the electronic level control (ELC) relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 10 | Go to Step 8 |
6 | Inspect for poor connections at the harness connector of the ESC module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 10 | Go to Step 9 |
7 | Repair the short to voltage in the ALC relay coil supply voltage circuit. Refer to Wiring Repairs . Did you complete the repair? | Go to Step 10 | -- |
8 | Replace the ELC relay. Did you complete the replacement? | Go to Step 10 | -- |
9 | Replace the ESC module. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 10 | -- |
10 |
Does the DTC reset? | Go to Step 2 | System OK |
