Keyless Entry Module

The Sentry Key REmote Entry Module (SKREEM) (3) (also known as the Sentry Key Immobilizer Module/SKIM or the Wireless Control Module/WCM) is the primary component of the Sentry Key Immobilizer System (SKIS). It is also the receiver for the Remote Keyless Entry (RKE) system and the Tire Pressure Monitor (TPM) system. The SKREEM is located on the right side of the steering column near the ignition lock cylinder housing and is concealed beneath the column shrouds. The molded black plastic housing for the SKREEM has an integral molded plastic halo-like antenna ring (1) that extends from one side. When the SKREEM is properly installed, the antenna ring is oriented around the circumference of the ignition lock cylinder housing.

A single integral connector receptacle (4) is located adjacent to the antenna ring on the SKREEM housing. An integral molded plastic mounting tab (2) on the SKREEM housing has a hole in the center through which a screw passes to secure the unit to the steering column lock housing. The SKREEM is connected to the vehicle electrical system through a single take out and connector of the instrument panel wire harness.

The SKREEM cannot be adjusted or repaired. If ineffective or damaged, the entire SKREEM unit must be replaced.

The Sentry Key REmote Entry Module (SKREEM) (also known as the Sentry Key Immobilizer Module/SKIM or the Wireless Control Module/WCM) contains a Radio Frequency (RF) transceiver and a microprocessor. The SKREEM transmits RF signals to, and receives RF signals from the Sentry Key transponder through a tuned antenna enclosed within the molded plastic antenna ring integral to the SKREEM housing. If this antenna ring is not mounted properly around the ignition lock cylinder housing, communication problems between the SKREEM and the transponder may arise. These communication problems will result in Sentry Key transponder-related faults.

The SKREEM also serves as the Remote Keyless Entry (RKE) RF receiver and, if the vehicle is so equipped, the receiver for the Tire Pressure Monitoring (TPM) system. Refer to DESCRIPTION for power locks, or DESCRIPTION for Tire Pressure Monitoring. The SKREEM communicates over the Controller Area Network (CAN) data bus with the ElectroMechanical Instrument Cluster (EMIC) (also known as the Cab Compartment Node/CCN), the Powertrain Control Module (PCM), the Totally Integrated Power Module (TIPM) or the diagnostic scan tool.

The SKREEM and the PCM both use software that includes a rolling code algorithm strategy, which helps to reduce the possibility of unauthorized Sentry Key Immobilizer System (SKIS) disarming. The rolling code algorithm ensures security by preventing an override of the SKIS through the unauthorized substitution of the SKREEM or the PCM. However, the use of this strategy also means that replacement of either the SKREEM or the PCM units will require a system initialization procedure to restore system operation.

The SKREEM retains in memory the ID numbers of any Sentry Key transponder that is programmed into it. A maximum of eight Sentry Key transponders can be programmed into the SKREEM. For added system security, each SKREEM is programmed with a unique Secret Key code. This code is stored in memory, sent over the CAN data bus to the PCM, and is encoded to the transponder of every Sentry Key that is programmed into the SKREEM. Therefore, the Secret Key code is a common element that is found in every component of the SKIS.

Another security code, called a PIN, is used to gain access to the SKREEM Secured Access Mode. The Secured Access Mode is required during service to perform the SKIS initialization and Sentry Key transponder programming procedures. The SKREEM also stores the Vehicle Identification Number (VIN) in its memory, which it learns through a CAN data bus message from the PCM during SKIS initialization.

In the event that a SKREEM replacement is required, the Secret Key code can be transferred to the new SKREEM from the PCM using the diagnostic scan tool and the SKIS initialization procedure. Proper completion of the SKIS initialization will allow the existing Sentry Keys to be programmed into the new SKREEM so that new keys will not be required. In the event that the original Secret Key code cannot be recovered, SKREEM replacement will also require new Sentry Keys. The diagnostic scan tool will alert the technician during the SKIS initialization procedure if new Sentry Keys are required.

When the key is inserted into the ignition switch and when the ignition switch is turned to the ON position, the SKREEM transmits an RF signal to excite the transponder in the ignition key. The SKREEM then waits for an RF signal response from the transponder. If the response received identifies the key as valid, the SKREEM sends an electronic valid key message over the CAN data bus. If the response received identifies the key as invalid or if no response is received from the key transponder, the SKREEM sends an invalid key message. 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 an invalid key ; therefore, if no message is received from the SKREEM by the PCM, the engine will be disabled and the vehicle immobilized after two seconds of running.

The SKREEM also sends electronic security indicator request messages to the EMIC over the CAN data bus to tell the EMIC how to operate the security indicator. The security indicator request message from the SKREEM tells the EMIC to turn the indicator ON for about three seconds each time the ignition switch is turned to the ON position as a bulb test. After completion of the bulb test, the SKREEM sends security indicator request messages to the EMIC to turn the indicator OFF, turn the indicator ON, or to flash the indicator ON and OFF. If the security indicator flashes or stays ON solid after the bulb test, it signifies a SKIS fault. If the SKREEM detects a system malfunction or the SKIS has become ineffective, the security indicator will stay ON solid. If the SKREEM detects an invalid key or if a key transponder-related fault exists, the

security indicator will flash. If the vehicle is equipped with the Customer Learn transponder programming feature, the SKREEM will also send messages to the EMIC to flash the security indicator whenever the Customer Learn programming mode is being utilized. See STANDARD PROCEDURE.

The SKIS performs a self-test each time the ignition switch is turned to the ON position, and will store fault information in the form of a Diagnostic Trouble Code (DTC) in SKREEM memory if a system malfunction is detected. The hard wired circuits of the SKREEM may be diagnosed using conventional diagnostic tools and procedures. However, conventional diagnostic methods will not prove conclusive in the diagnosis of the SKREEM or the electronic controls or communication between other modules and devices that provide some features of the SKIS. The most reliable, efficient, and accurate means to diagnose the SKREEM or the electronic controls and communication related to SKREEM operation requires the use of a diagnostic scan tool.

WARNING: To avoid serious or fatal injury on vehicles equipped with airbags, disable the Supplemental Restraint System (SRS) before attempting any steering wheel, steering column, airbag, Occupant Classification System (OCS), seat belt tensioner, impact sensor, or instrument panel component diagnosis or service. Disconnect and isolate the battery negative (ground) cable, then wait two minutes for the system capacitor to discharge before performing further diagnosis or service. This is the only sure way to disable the SRS. Failure to take the proper precautions could result in accidental airbag deployment.

1. Disconnect and isolate the battery negative cable. 2. Remove but do not disconnect the right multi-function switch from the integral mounting bracket (1) on the right side of the clockspring and position it so that the Sentry Key REmote Entry Module (SKREEM) (also known as the Sentry Key Immobilizer Module/SKIM or the Wireless Control Module/WCM)

mounting screw (2) may be accessed. Refer to REMOVAL . 3. Disconnect the instrument panel wire harness connector (4) from the SKREEM (3) connector receptacle. 4. Remove the screw that secures the SKREEM to the boss on the top of the ignition lock cylinder housing (5). 5. Disengage the SKREEM antenna ring from around the ignition lock housing and remove the SKREEM from the steering column.

WARNING: To avoid serious or fatal injury on vehicles equipped with airbags, disable the Supplemental Restraint System (SRS) before attempting any steering wheel, steering column, airbag, Occupant Classification System (OCS), seat belt tensioner, impact sensor, or instrument panel component diagnosis or service. Disconnect and isolate the battery negative (ground) cable, then wait two minutes for the system capacitor to discharge before performing further diagnosis or service. This is the only sure way to disable the SRS. Failure to take the proper precautions could result in accidental airbag deployment.

1. Position the Sentry Key REmote Entry Module (SKREEM) (3) (also known as the Sentry Key Immobilizer Module/SKIM or the Wireless Control Module/WCM) onto the steering column ignition lock housing with the antenna ring oriented around the lock cylinder (5). 2. Install and tighten the screw (2) that secures the SKREEM mounting bracket to the boss on the top of the ignition lock housing. Tighten the screw to 2 N.m (20 in. lbs.). 3. Reconnect the instrument panel wire harness connector (4) to the SKREEM connector receptacle. 4. Reinstall the right multi-function switch onto the integral mounting bracket (1) on the right side of the

clockspring. Refer to INSTALLATION . 5. Reconnect the battery negative cable.

NOTE: On vehicles equipped with the Sentry Key Immobilizer System (SKIS), when the SKREEM is replaced with a new unit, a diagnostic scan tool MUST be used to initialize the new SKREEM and to program at least two Sentry Key transponders before the vehicle can be operated. See STANDARD PROCEDURE.

NOTE: On vehicles equipped with a Tire Pressure Monitoring (TPM) system and a full- sized matching spare tire and wheel assembly, when the SKREEM or the spare tire pressure sensor is replaced with a new unit, a diagnostic scan tool MUST be used to run a routine that allows the SKREEM to be programmed with the ID number and location of the spare tire pressure sensor mounted in the wheel of the spare tire. This may be done using a TPM-RKE Analyzer special tool by following the programming steps outlined in the diagnostic scan tool for Program Tire Sensor ID w/TPM Tool under Miscellaneous Functions for the WCM/Wireless Control Module menu item. If a TPM-RKE Analyzer special tool is not available, the spare tire must be dismounted from its wheel to access and note the ID number on the spare tire pressure sensor so that the ID code for that sensor can be programmed into the new SKREEM. Follow the programming steps outlined in the diagnostic scan tool for Learn Spare Tire Sensor ID also found under Miscellaneous Functions for the WCM/Wireless Control Module menu item. Refer to INSTALLATION .

SIREN