Grand Cherokee 2WD Limited V8-4.7L (2002)
The heater elements inside the seat back and cushion are different for the Limited and Laredo models. The Laredo seat heater elements are wired
in series whereas the Limited seat elements are wired in parallel. This means that if an element is open in a Laredo model there will be no heater
output to either the cushion or the seat back. If an element is open in a Limited model, the other elements will operate as usual. However, if one of
the elements is open, the seat cushion will have to be replaced.
There are three heater elements in the seat cushions for both models. The Laredo uses a resistor wire for its center and both side bolsters (raised
outer side panels) and the Limited uses a carbon fiber element for its center and resistor wire for the bolsters.
SENTRY KEY IMMOBILIZER SYSTEM (SKIS)
The Sentry Key Immobilizer System (SKIS) is an immobilizer system designed to prevent unauthorized vehicle operation. The system consists of
a Sentry Key Immobilizer Module (SKIM), ignition key(s) equipped with a transponder chip and engine controller. When the ignition switch is
turned ON, the SKIM interrogates the ignition key. If the ignition key is 'Valid" the SKIM sends a PCI Bus message to the engine controller
indicating the presence of a valid ignition key. Upon receiving a "Valid" key signal the PCM/ECM will allow the engine to continue to operate.
For additional information on the SKIS, refer to the appropriate Powertrain Diagnostic information.
POWER SUNROOF
The power sunroof in the Grand Cherokee is 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.
Part 3B
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. 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/WG:
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Body Control Module
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Adjustable Pedals 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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Engine Control Module (Diesel)
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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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Seat Module
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Electronic Vehicle Information Center
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Mechanical Instrument Cluster
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Shifter Assembly (Diesel)
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Rain Sensor
-
Power Amplifier
-
Intrusion Transceiver Module (Export)
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.
