Grand Cherokee 2WD V8-4.7L VIN N (2000)
The secret key and challenge are plugged into an algorithm that produces the encrypted response message. The transponder uses the crypto
algorithm to receive, decode and respond to the message sent by SKIM. After responding to the coded message, the transponder sends a
transponder I.D. message to the SKIM. The SKIM compares the transponder I.D. to the available valid key codes in SKIM memory (8 key
maximum). After validating the key the SKIM sends a PCI Bus message called a "Seed Request" to the PCM then waits for a controller response.
If the PCM does not respond, the SKIM will send the seed request again. After three failed attempts the SKIM will stop sending the seed request
and store a trouble code. If the PCM sends a seed response, the SKIM sends a valid/invalid key message to the PCM. This is an encrypted message
that is generated using the following:
VIN - Vehicle Identification Number
Seed - This is a random number that is generated by the PCM at each ignition key cycle.
The VIN and seed are plugged into a rolling code algorithm that encrypts the "valid/invalid key" message. The PCM uses the rolling code
algorithm to receive, decode an respond to the valid/invalid key message sent by SKIM. After sending the valid/ invalid key message the SKIM
waits 3.5 seconds for a PCM status message from the PCM. If the PCM does not respond with a valid key message to the SKIM, a fault is detected
and a trouble code stored.
The SKIS incorporates a warning lamp located in the instrument cluster. The lamp is actuated when the SKIM sends a PCI Bus message to the
instrument cluster requesting the lamp ON. The SKIM will request lamp operation for the following:
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bulb check at ignition ON
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to alert the vehicle operator to a SKIS malfunction
For all faults except transponder faults and VIN mismatch, the lamp remains on steady. In the event of a transponder fault the light flashes at the
rate of 1 Hz (once per second). If a fault is present the lamp will remain ON or flashing for the complete ignition cycle. If a fault is stored in
SKIM memory which prevents the system from operating properly, the PCM will allow the engine to start and run (for 2 seconds) up to six times.
After the sixth attempt, the PCM disables the starter relay until the fault is corrected.
For additional information on the SKIS, refer to the appropriate "Powertrain Diagnostic Information".See: Testing and Inspection
POWER SUNROOF
The power sunroof in the 2000 Grand Cherokee is now controlled by the Body Control Module (BCM). After the ignition has been turned OFF,
the power sunroof will remain operational for an additional 45 seconds. If the front doors are opened during this time, the BCM will remove
power from the sunroof.
COMMUNICATION
The Programmable Communication Interface or PCI Bus is a single wire multiplexed network capable of supporting binary encoded messages
shared between multiple modules. The PCI bus circuit is identified as D25 and is yellow with a violet tracer. Additional tracer colors may be
added to the violet in order to distinguish between different module connections. The modules are wired in parallel. Connections are made in the
harness using splices.
One splice called the Diagnostic Junction Port, serves as the "Hub" of the bus. The Diagnostic Junction Port provides an access point to isolate
most of the modules on the bus in order to assist in diagnosing the circuit. The following modules are used on the WJ:
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Body Control Module
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Door Modules (Driver & Passenger)
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Airbag Control Module
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Controller Antilock Brake
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Powertrain Control Module
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Radio
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CD Changer
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Transmission Control Module
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Automatic Zone Control Module
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Sentry Key Immobilizer Module
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Memory and/or Heated Seats Module
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Electronic Vehicle Information Center
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Mechanical Instrument Cluster
Each module provides its own bias and termination in order to transmit and receive messages. The bus voltage is at zero volts when no modules
are transmitting and is pulled up to about seven and a half volts when modules are transmitting.
