Sentry Key Immobilizer

WARNING: This page is about a different car, the 2004 Dodge Grand Caravan, 2004 Dodge Caravan, and 2004 Chrysler Town & Country. However, it is still accessible from the selected car via links, so may be relevant.

The Sentry Key Remote Entry Module (SKREEM) receives an encrypted Radio Frequency (RF) signal from the transponder key. The SKREEM then decrypts the signal and broadcasts the requested remote commands to the appropriate modules in the vehicle over the Programmable Communication Interface (PCI) data bus. A valid transponder key ID must be incorporated into the RF signal in order for the SKREEM to pass the message on to the appropriate modules.

Automatic transponder key synchronization is done by the SKREEM if a valid transponder key is inserted into the ignition cylinder, and the ignition is turned ON. This provides a maximum operation window for RKE functions.

Each Sentry Key Remote Entry System (SKREES) consists of a SKREEM and a transponder key. Each system has a secret key code unique to that system. The secret key is electronically coded in the SKREEM and in all programmed transponder keys. It is used for immobilization and RKE functions for data security. In addition, each transponder key will have a unique identification.

When the ignition switch is moved to the RUN position, the SKREEM transmits an Radio Frequency (RF) signal to the transponder in the ignition key. The SKREEM then waits for a response RF signal from the transponder in the key. If the response received identifies the key as valid, the SKREEM sends a "valid key" message to the Powertrain Control Module (PCM) over the Programmable Communication Interface (PCI) data bus. If the response received identifies the key as invalid or no response is received from the transponder in the ignition key, the SKREEM sends an "invalid key" message to the PCM. The PCM will enable or disable engine operation based upon the status of the SKREEM messages. It is important to note that the default condition in the PCM is "invalid key." Therefore, if no response is received by the PCM, the engine will be immobilized after two (2) seconds of running.

The SKREEM also sends indicator light status messages to the Mechanical Instrument Cluster (MIC) to operate the light. This is the method used to turn the light ON solid or to flash it after the indicator light test is complete to signify a fault in the SKREES. If the light comes ON and stays ON solid after the indicator light test, this signifies that the SKREEM has detected a system malfunction and/or that the SKREES has become inoperative. If the SKREEM detects an invalid key OR a key-related fault exists, the indicator light will flash following the indicator light test. The SKREEM may also request an audible chime if the customer key programming feature is available and the procedure is being utilized (Refer to STANDARD PROCEDURE - TRANSPONDER PROGRAMMING ).