Alarm System Transponder: Description and Operation

TRANSPONDER KEY

Transponder Key:

The Sentry Key Immobilizer System (SKIS) which communicates with the Sentry Key Remote Entry Module (SKREEM), uses a transponder chip that is integral to each key fob. Ignition keys are supplied with the vehicle when it is shipped from the factory. The transponder chip is located within the Remote Keyless Entry (RKE) fob.

Each Sentry Key has a unique transponder identification code permanently programmed into it by the manufacturer. Likewise, the Sentry Key Remote Entry Module (SKREEM) has a unique "Secret Key" code programmed into it by the manufacturer as well. When a Sentry Key is programmed into the memory of the SKREEM, the SKREEM stores the transponder identification code from the Sentry Key, and the Sentry Key learns the "Secret Key" code from the SKREEM. Once the Sentry Key learns the "Secret Key" code of the SKREEM, it is also permanently programmed into the transponder's memory.

The Sentry Key's transponder is within the range of the SKREEM's transponder ring when it is inserted into the ignition lock cylinder. When the ignition switch is turned to the ON position, the SKREEM communicates with the Sentry Key via a radio frequency (RF) signal. The SKREEM determines if a valid key is present based on the information it receives from the Sentry Key. If a valid key is detected, that fact is communicated to the Engine Control Module (ECM) via the Controller Area Network (CAN) data bus and the vehicle is allowed to continue running. If an invalid key is received by the ECM or no status at all is communicated, the vehicle will stall after two (2) seconds of running. The indicator light will be flashing at this point. The Sentry Key's transponder can not be repaired. If it is faulty or damaged, it must be replaced.

Common communication problems:
- Two transponder keys too close together.
- Speed Pass too close to transponder key. Solid indicator that there is a system failure.
- Loss of ECM communication.
- Failed transponder ring circuit.