Grand Cherokee 2WD Limited V8-4.7L (2002)
Exterior Lighting Battery Saver
The BCM monitors the status of and controls the park lamp, head lamp and fog lamp relay's. If any exterior lamps are left ON after the ignition is
turned OFF, the BCM will turn them OFF after 8 minutes.
Headlamp Delay
The headlamp time delay operates when the ignition switch is turned OFF while the headlamps are still ON. This feature is customer
programmable to provide a 30, 60 or 90 second time delay before turning OFF the headlamps. This feature can also be disabled.
Headlamp Switch
The headlight switch on WJ vehicles uses a multiplexed (MUX) circuit to the BCM. The BCM will then control the park lamp, low/high head
lamp and fog lamp relay's based on this input.
Fog Lamp Control
The body control module controls the operation of the fog lamp relay which controls the fog lamps. The fog lamps can only be ON if the park or
low beam headlamps are ON. If the high beams are turned ON, the fog lamps will automatically be turned OFF.
INTERIOR LIGHTING
Courtesy Lamp Control
The body controller has direct control over all of the vehicle's courtesy lamps. The body computer will illuminate the courtesy lamps under any of
the following conditions:
1. Any door is ajar and courtesy lamp switch on the left multi-function switch is not in the dome OFF position.
2. The courtesy lamp switch on the left multi-function switch is in the dome ON position.
3. A Remote Keyless entry unlock message is received.
4. Driver door unlocked with key (with VTSS only).
Illuminated Entry
Illuminated entry will be initiated when the customer enters the vehicle by unlocking the doors with the key fob, or with the key if the vehicle is
equipped with vehicle theft alarm. Upon exiting the vehicle, if the lock button is pressed with a door open, illuminated entry will cancel when the
door closes. If the doors are closed and the ignition switch is turned ON, the illuminated entry also cancels. The illuminated entry feature will not
operate if the courtesy lamp switch is in the dome OFF position.
Interior Lighting Battery Saver
If any of the interior lamps are left ON after the ignition is turned OFF, the BCM will turn them OFF after 8 minutes. To return to normal
operation, the courtesy lamps will operate after the dome lamp switch or door ajar switch changes state. The glove box, switched reading lamps
and vanity lamps require that the ignition be turned to the ON/ACC position.
ELECTRO/MECHANICAL INSTRUMENT CLUSTER (EMIC)
The Instrument Cluster contains a Fuel, Voltmeter, Coolant Temp, and Oil Pressure gauge, a Tachometer and a Speedometer. With the exception
of the Voltmeter, the cluster positions the gauges with PCI Bus messages received from the PCM. The Voltmeter operates directly OFF of the
Fused B+ Switched Ignition Output circuit that supplies ignition voltage for the cluster.
The Instrument Cluster also contains warning indicators that are illuminated by hard wired inputs or by messages received from other modules on
the PCI Bus.
The Trip/Total Odometer is a Vacuum Fluorescent Display (VF) that is controlled by PCI Bus messages received from the PCM.
The cluster illumination lamps are hard wired in the Instrument Cluster. When the Park or Headlamps are turned ON, the cluster receives a
dimmed battery feed from the Headlamp Switch. The cluster I/O Processor controls the VF display dimming and also sends dimming level
messages on the PCI Bus.
The EMIC will communicate with the DRB III to display PCI Engine Info, PCI Bus Info, and certain input/outputs. Cluster diagnostic capabilities
that the DRB III will actuate is limited to the Cluster Calibration Points for the gauges. The DRB III can also extract active and stored Diagnostic
Trouble Codes (DTC) from the Instrument Cluster.
The EMIC is also capable of performing a diagnostic Self-Test that is actuated by depressing and holding the Odometer trip reset stalk while
cycling the ignition from the OFF to the ON position. After the cluster Odometer displays CHEC, releasing the reset stalk begins the test. The
cluster will then position all of the gauges at specified calibration points and will illuminate all the PCI Bus controlled indicators. The cluster will
also illuminate each segment of the VF display.
The EMIC can verify communications with the PCM, ID the module, or change the country code using the DRB III.
Instrument Panel Dimming
I/P dimming is accomplished using the body computer. The panel dimming level switch is read by the body computer which converts the level to a
value that is sent over the PCI bus. Other modules such as the Radio, MIC, and the EVIC use this data so their display intensity matches the other
