• 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 an ignition key is inserted into the ignition lock cylinder and the ignition is switched ON, the transponder embedded in the key is energized by the exciter coil surrounding the ignition lock cylinder. The transponder transmits a signal to the body control module (BCM). The BCM then compares this value to a value stored in memory. If the value is correct, the BCM will send the prerelease password via the serial data circuit to the engine control module (ECM). If the learned key code does not match or a transponder value is not received, the BCM will send the start disable password to the ECM.

When a keyless entry transmitter is inserted into the transmitter pocket/slot and the ignition mode switch is pressed, the transponder embedded in the transmitter is energized by the immobilizer antenna exciter coil. The transponder transmits a signal to the body control module (BCM). The BCM then compares this value to a value stored in memory. If the value is correct, the BCM will send the prerelease password via the serial data circuit to the engine control module (ECM). If the learned key code does not match or a transponder value is not received, the BCM will send the start disable password to the ECM.

Ignition is in the Accessory or Run position.

The transponder value measured by the BCM is incorrect or not learned to the vehicle.

• Vehicle starting will be disabled.
• The security indicator in the instrument cluster will be illuminated. The driver information center will display a service message.

• A current DTC will be cleared when the BCM detects a valid transponder value from the ignition key.
• A history DTC will be cleared after 100 malfunction-free ignition cycles.

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. Perform the Replacing Keys procedure. Refer to Key with Integrated Transmitter Programming.
2. Verify the K9 Body Control Module learns the vehicle key. The scan tool Master Keys Learned parameter should increment to indicate another key has been learned.
• If the BCM does not learn the key

  Replace the key.

• If the BCM learns the key
3. All OK.