RAM 1500 Truck 4WD V8-5.7L VIN D (2005)
Alarm System Transponder: Description and Operation
Each ignition key (4) used in the Sentry Key Immobilizer System (SKIS) has an integral transponder chip (2) concealed beneath the molded rubber cap
(1), where it is secured within a plastic mount in the head (3) of the metal key. In addition to having to be cut to match the mechanical coding of the
ignition lock cylinder, each new Sentry Key has a unique transponder identification code that is permanently programmed into it by the manufacturer,
and which must be programmed into the Sentry Key Immobilizer Module (SKIM) to be recognized as a valid key. The Sentry Key transponder cannot be
adjusted or repaired. If faulty or damaged, the entire key and transponder unit must be replaced.
When the ignition switch is turned to the On position, the Sentry Key Immobilizer Module (SKIM) communicates through its antenna with the Sentry
Key transponder using a Radio Frequency (RF) signal. The SKIM then listens for a RF response from the transponder through the same antenna. The
Sentry Key transponder chip is within the range of the SKIM transceiver antenna ring when it is inserted into the ignition lock cylinder. The SKIM
determines whether a valid key is present in the ignition lock cylinder based upon the response from the transponder. If a valid key is detected, that fact
is communicated by the SKIM to the Powertrain Control Module (PCM) over the Programmable Communications Interface (PCI) data bus, and the
PCM allows the engine to continue running. If the PCM receives an invalid key message, or receives no message from the SKIM over the PCI data bus,
the engine will be disabled after about two seconds of operation. The ElectroMechanical Instrument Cluster (EMIC) will also respond to the invalid key
message on the PCI data bus by flashing the security indicator on and off.
Each Sentry Key has a unique transponder identification code permanently programmed into it by the manufacturer. Likewise, the SKIM has a unique
Secret Key code programmed into it by the manufacturer. When a Sentry Key is programmed into the memory of the SKIM, the SKIM stores the
transponder identification code from the Sentry Key, and the Sentry Key learns the Secret Key code from the SKIM. Once the Sentry Key learns the
Secret Key code of the SKIM, it is permanently stored in the memory of the transponder. Therefore, once a Sentry Key has been programmed to a
particular vehicle, it cannot be used on any other vehicle.
The SKIS performs a self-test each time the ignition switch is turned to the On position, and will store key-related fault information in the form of
Diagnostic Trouble Code (DTC) in SKIM memory if a Sentry Key transponder problem is detected. The Sentry Key transponder chip can be diagnosed,
and any stored DTC can be retrieved using a diagnostic scan tool.
