• 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.

For symptom byte information, refer to Symptom Byte List.

When certain modules are programmed and configured during installation, the module learns a specific environment identifier which is unique to the vehicle. The environment identifier is used to prevent the swapping of control modules between vehicles. The body control module (BCM) is the keeper of the environment identifier. The instrument cluster, electronic brake control module, HVAC control module, inflatable restraint sensing and diagnostic Module, and telematics communication interface control module each learn the environment identifier during their configuration process. During vehicle operation, the BCM sends the immobilizer identifier as a challenge and each module responds to the challenge by sending the environment identifier back to the BCM. If the BCM does not send an immobilizer identifier or no environment identifiers are received, vehicle starting is disabled.

Ignition is in the ACCESSORY or RUN position.

No environment identifier was received by the BCM.

• The security indicator in the instrument cluster will illuminate.
• Vehicle starting will be disabled.

A current DTC will be cleared when the module learns a correct environment identifier and it is received by the BCM.

Immobilizer Schematics

Master Electrical Component List

Immobilizer Description and Operation

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

Control Module References for scan tool information

1. Verify DTC U0100–U02FF is not set.
• If any of the DTCs are set

  Refer to Diagnostic Trouble Code (DTC) List - Vehicle

• If none of the DTCs are set
2. Perform the Programming and Setup procedure for the control module that the DTC is setting against based on the DTC descriptor.
3. Verify the DTC does not set after programming.
• If the DTC sets after programming

  Replace the control module that the DTC is setting against based on the DTC descriptor.

• If the DTC does not set after programming
4. All OK.

Perform the Diagnostic Repair Verification after completing the repair.

Control Module References for control module programming, and setup.