Body Control Module (BCM)

The immobilizer system is an integral part of the BCM and is controlled internally within the BCM. The BCM can learn up to 8 keys (transponder values).

The BCM uses the following inputs:

• Environment identifier exchange with various modules
• Encrypted code from the vehicle key, received by the Immobilizer Control Module
• Encrypted code from the vehicle key, received by the Remote Control Door Lock Receiver (with BTM)

The BCM uses the following outputs:

• Prerelease password communication with ECM
• Challenge/response with ECM

When a transponder value is received by the BCM, the BCM will compare this value to the learned key code stored in memory. The BCM then performs one of the following functions:

• If the encrypted code value matches the values stored in the BCM memory, the BCM will send the prerelease password to the ECM via serial data.
• If the encrypted code unique value does not match the value stored in the BCM, the BCM will send the start disable message to the ECM via serial data.
• If the BCM is unable to measure the ignition key encrypted code value, the BCM will not send any messages to the ECM.