GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

    •  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.

DTC Descriptor

DTC C0550 39: Electronic Control Unit (ECU) Performance

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Electronic Control Unit (ECU) Performance

--

--

--

C0550 39

Circuit/System Description

The coupling control module (CCM) detects an internal malfunction.

Conditions for Running the DTC

The ignition switch is in the ON position.

Conditions for Setting the DTC

An internal EBCM malfunction exists.

Action Taken When the DTC Sets

One or more of the following actions may occur:

    • All Wheel Drive Off (AWD Disabled).
    • Service All Wheel Drive (Service AWD).

Conditions for Clearing the DTC

    • The condition for the DTC is no longer present.
    • The DTC is not detected in 100 consecutive drive cycles.

Reference Information

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Scan Tool Data List for CCM

Circuit/System Verification

DTC C0550 will set as result of internal (CCM) circuit failure.

Replace the CCM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for CCM.

Diagnostic Instructions

    •  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.

DTC Descriptor

DTC C0550 39: Electronic Control Unit (ECU) Performance

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Electronic Control Unit (ECU) Performance

--

--

--

C0550 39

Circuit/System Description

The coupling control module (CCM) detects an internal malfunction.

Conditions for Running the DTC

The ignition switch is in the ON position.

Conditions for Setting the DTC

An internal EBCM malfunction exists.

Action Taken When the DTC Sets

One or more of the following actions may occur:

    • All Wheel Drive Off (AWD Disabled).
    • Service All Wheel Drive (Service AWD).

Conditions for Clearing the DTC

    • The condition for the DTC is no longer present.
    • The DTC is not detected in 100 consecutive drive cycles.

Reference Information

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Scan Tool Data List

Circuit/System Verification

DTC C0550 will set as result of internal (CCM) circuit failure.

Replace the CCM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for CCM replacement, setup, and programming