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For 1990-2009 cars only

Circuit Description W/F45

The automatic level control (ALC) 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

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 3 consecutive ignition cycles, or during the same ignition cycle after clearing the DTC with a scan tool.

DTC 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.

  1. This step tests for voltage in the Automatic Level Control relay coil supply voltage circuit.

  2. 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

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

  1. Disconnect the electronic suspension control (ESC) module connector.
  2. Turn ON the ignition, with the engine OFF.
  3. Connect a test lamp between the automatic level control (ALC) relay coil supply voltage circuit and a good ground.

Does the test lamp illuminate?

Go to Step 3

Go to Step 4

3

  1. Turn OFF the ignition.
  2. Disconnect the electronic level control (ELC) Relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Connect a test lamp between the ALC relay coil supply voltage circuit and a good ground.

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 in Wiring Systems.

Did you find and correct the condition?

Go to Step 10

Go to Step 5

5

Inspect for poor connections at the ELC Relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

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 in Wiring Systems.

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 in Wiring Systems.

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 in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 10

--

10

  1. Use the scan tool in order to clear the DTCs .
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

Go to Step 2

System OK