Sentry Key Immobilizer System (SKIS)

SENTRY KEY IMMOBILIZER SYSTEM (SKIS)
The SKIS is an immobilizer system designed to prevent unauthorized vehicle operation. The system consists of a Sentry Key Immobilizer Module (SKIM) and ignition key(s) called Sentry Key(s) which are equipped with a transponder chip. The SKIM communicates over the Programmable Communication Interface multiplex system (PCI) bus network to the Body Control Module (BCM) Powertrain Control Module (PCM) and/or the DRB scan tool.

When the ignition is turned to the Run/Start position the SKIM produces a Radio Frequency (RF) signal via an antenna which is located around the ignition lock cylinder. The RF powers up the transponder chip inside the Sentry Key. The transponder chip then emits a coded signal that is received by the SKIM antenna. If this coded signal is valid the SKIM sends a "VALID KEY" message to the PCM. If the first transponder signal is not valid the SKIM will attempt four more times to receive a correct transponder signal. If a valid signal is not received the SKIM stores a diagnostic trouble code and sends an "INVALID KEY" message to the PCM. Then the PCM will only allow the engine to start for two seconds then stall. This start and stall will be allowed up to six times after which the PCM will disable the starter relay.

The SKIS includes two valid Sentry Keys from the factory. If the customer wishes additional uncoded Sentry Key blanks are available. These blank keys must be cut to match a valid key but the engine will not start unless the transponder chip inside the blank key is programmed to that particular vehicle.

The Sentry Key Immobilizer System (SKIS) can be programmed to recognize a total of eight keys.

The SKIM sends messages to the Body Control Module (BCM) over the PCI bus to control the VTSS indicator lamp. The SKIM sends a message to the BCM to turn the lamp ON for about three seconds when the ignition is turned to the Run/Start position as a bulb test. If the indicator lamp comes ON and stays ON after the bulb test it indicates that the SKIM has detected a system malfunction and/or that the SKIS has become inoperative. If an invalid key is detected in the ignition key cylinder with the ignition switch in the Run/Start position or when the SKIM has entered its customer key programming mode the SKIM will flash the VTSS indicator lamp ON and OFF.

Sentry Key Immobilizer Trouble Codes
Typically modules have Diagnostic Trouble Codes that are referred to as either active or stored. In the case of the Sentry Key Immobilizer Module however all codes are stored codes. The two various types of stored codes in the SKIM can be considered to be either current or pre-existing codes. If more than one code exists diagnostic priority should be given to the current code(s). To determine what codes are current and what ones are pre-existing. Use the DRB to read SKIM Diagnostic Trouble Code(s) (DTC) and record them. Erase the SKIM DTC(s). Cycle the ignition OFF and then back to the Run/Start position. Leave it in that position for 3 minutes before attempting to read DTC(s). Read SKIM DTC(s) to verify that the code(s) displayed on the DRB are current faults. If no SKIM DTC(s) are present at this time proceed to the PRE-EXISTING DIAGNOSTIC TROUBLE CODES (DTC) DISPLAYED. A current code indicates a malfunction that is CURRENT at the time of vehicle service. A pre-existing code indicates the malfunction is not currently present. If a malfunction is not detected after 80 ignition cycles the code will automatically be erased.

Sentry Key Immobilizer Module Replacement and System Initialization Process
The Sentry Key Immobilizer Module (SKIM) Replacement and System Initialization Process can be summarized by the following:
1. Obtain the vehicle's unique PIN number assigned to it's original SKIM module from either the vehicle's invoice or from Daimler Chrysler's Customer Center.
2. With the DRB select "Theft Alarm " "Skim " "Miscellaneous." Select "SKIM Module Replaced" and the DRB will prompt you through the following steps.
3. Program the unique 4 digit PIN number into the SKIM's memory.
4. Program the vehicle's VIN number into the SKIM's memory.
5. Program the country code into the SKIM's memory (U.S.).
6. Transfer the vehicle's unique Secret Key data from the PCM. This process Will require the SKIM module to be in secured access mode. The PIN number must be entered into the DRB before the SKIM Will enter secured access mode. Once secured access mode is active the SKIM will remain in that mode for 60 seconds.
7. Program all customer keys into the SKIM's memory. This requires that the SKIM be in secured access mode. The SKIM module will immediately exit secured access mode after each key is programmed. Note: Secured access mode is not required to query the programmed status of the key

NOTE 1: IF A PCM IS REPLACED THE UNIQUE SECRET KEY DATA MUST BE TRANSFERRED FROM THE SKIM MODULE TO THE PCM. THIS PROCEDURE REQUIRES THE SKIM TO BE PLACED IN SECURED ACCESS MODE USING THE FOUR DIGIT PIN CODE.

NOTE 2: IF THREE ATTEMPTS ARE MADE TO ENTER SECURED ACCESS MODE USING AN INCORRECT PIN SECURED ACCESS MODE WILL BE LOCKED OUT FOR ONE HOUR. TO EXIT THIS LOCK OUT MODE LEAVE THE IGNITION SWITCH IN THE RUN POSITION CONTINUOUSLY FOR ONE HOUR. (ENSURE ALL ACCESSORIES ARE TURNED OFF. ALSO MONITOR THE BATTERY STATE AND CONNECT A BATTERY CHARGER IF NECESSARY).

To program Sentry Keys using the "customer programming" method which requires two valid Sentry Keys refer to either the owner's manual or the proper procedure.

Programming Blank Sentry Keys With The DRB III
When programming a blank Sentry Key transponder the key blank must first be cut to match the ignition lock cylinder. It will also be necessary to enter the vehicle's 4-digit PIN code into the DRB to enter the SKIM's secured access mode.

NOTE: ONCE A SENTRY KEY IS PROGRAMMED TO A PARTICULAR VEHICLE IT CANNOT BE TRANSFERRED TO ANOTHER VEHICLE.

Insert the blank key into the ignition and turn it to the Run/Start position. Using the DRB select "Theft Alarm" then "SKIM" then "Miscellaneous". Select "Program New Key." Enter the 4-digit PIN code using the DRB. When programming is completed the SKIM will exit secured access mode and display the status of the key. The different status messages are (programming successful learned key in ignition maximum key limit exceeded programming not attempted or programming failed).

"Programming Successful" is displayed if SKIM Sentry Key programming succeeds.

"Learned Key in Ignition" is displayed if the key in the ignition has already been programmed into that vehicle's SKIM.

"8 Keys Already Learned (At The Maximum) Programming Not Done" is displayed if eight keys have already been programmed into the SKIM. In this case if a new key needs to be added due to a lost or defective key the "Erase All Keys" function (requires entering secured access mode) has to be performed. Then the customer's seven keys plus the new key MUST be reprogrammed into the SKIM.

"Programming Key Failed" is displayed if further diagnosis is required.

To learn additional keys turn the ignition OFF remove the learned key and insert the next new blank key. Turn ignition to the Run position and re-enter the secured access mode function and repeat the "Program New Key" procedure outlined above.