Sentry Key Immobilizer System

The immobilizer authentication process is as listed:

1. When the Engine Start/Stop button is pressed.
2. The Radio Frequency Hub (RFH) and the Low Frequency (LF) antennas work together to authenticate the key fob.
3. If the key fob is authenticated as valid, the RFH sends an ignition request signal to the Body Control Module (BCM). However if the key fob is not authenticated, this process stops and the BCM does not receive the ignition request signal.
4. When the BCM receives the ignition request signal from the RFH, the BCM initiates the MiniKrypt code exchange with the RFH.
5. The RFH responds to the BCM MiniKrypt authentication challenge. If this exchange is unsuccessful, the BCM will stop processing the ignition command. If the exchange was successful, the BCM next determines if ESL is equipped on the vehicle.
6. If the vehicle is equipped with Electronic Steering Lock (ESL), the BCM will then send an unlock signal to the ESL. If the ESL is not able to successfully unlock, the BCM will stop processing the ignition command. If the ESL is able to successfully unlock, the ESL responds to the ESL unlock challenge.
7. When the BCM receives successful ESL unlock challenge response, the BCM sends a Controller Area Network-Chassis (CAN-C) ignition run/start command to the Powertrain Control Module (PCM) and then activates its own internal ignition relays.
8. The PCM initiates a MiniKrypt exchange between it and the BCM based on the run/start signal command sent from the BCM.
9. The BCM responds to the PCM request with a verification acknowledgment, thus allowing the PCM to start the engine. If for any reason that the PCM BCM MiniKrypt exchange was not successful, the PCM will shut the engine off after two seconds and report this back to the BCM. If the exchange is successful, the engine will continue to run.

If the authentication between the BCM and PCM has failed, a new ignition cycle is required to being the process once again. The PCM will allow up to 6 consecutive engine running attempts before it disables the starter motor and requires that a new key be authenticated.

The BCM controls the IPC immobilizer warning lights. When the ignition state changes to RUN or START, the BCM sends a command to the Instrument Panel Cluster (IPC) to illuminate the immobilizer indicator for 3 seconds. The BCM keeps the indicator lamp off unless there is an unsuccessful validation. At this point, the BCM commands the IPC to illuminate the immobilizer indicator.