Grand Cherokee 2WD V8-4.7L VIN J (2004)
Shift Indicator: Description and Operation
SHIFT INDICATOR (TRANSFER CASE)
A part time indicator is standard equipment on all instrument clusters, but is only functional on vehicles equipped with the standard equipment
SelecTrac four-wheel drive system. The part time indicator is located near the right edge of the instrument cluster, to the right of the speedometer. The
part time indicator consists of the words "PART TIME" imprinted on an amber lens. The lens is located behind a cutout in the opaque layer of the
instrument cluster overlay. The dark outer layer of the overlay prevents the indicator from being clearly visible when it is not illuminated. The words
"PART TIME" appear silhouetted against an amber field through the translucent outer layer of the overlay when the indicator is illuminated from
behind by a replaceable incandescent bulb and bulb holder unit located on the instrument cluster electronic circuit board. The part time indicator lens
is serviced as a unit with the instrument cluster lens, hood and mask unit.
The part time indicator gives an indication to the vehicle operator that a four-wheel drive part time operating mode of the transfer case is selected. On
vehicles with the standard equipment Selec-Trac four-wheel drive system, the part time indicator illuminates when the NV-242 transfer case is
engaged in either the 4 X 4 Part Time or 4 Lo positions. This indicator is controlled by a transistor on the instrument cluster electronic circuit board
based upon cluster programming and electronic messages received by the cluster from the Powertrain Control Module (PCM) over the Programmable
Communications Interface (PCI) data bus. The part time indicator bulb is completely controlled by the instrument cluster logic circuit, and that logic
will only allow this indicator to operate when the instrument cluster receives a battery current input on the fused ignition switch output (RUN/START)
circuit. Therefore, the indicator will always be OFF when the ignition switch is in any position except ON or Start. The bulb only illuminates when it
is provided a path to ground by the instrument cluster transistor. The instrument cluster will turn ON the part time indicator for the following reasons:
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Part Time Indicator lamp-ON Message - Each time the cluster receives a part time indicator lamp-ON message from the PCM indicating that a
four-wheel drive part time position of the transfer case has been selected, the part time indicator will be illuminated. The indicator remains
illuminated until the cluster receives a part time indicator lamp-OFF message from the PCM.
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Actuator Test - Each time the cluster is put through the actuator test, the part time indicator will be turned ON for the duration of the test to
confirm the functionality of the bulb and the cluster control circuitry.
The PCM continually monitors the transfer case switch to determine the driveline operating mode. The PCM then sends the proper part time indicator
lamp-ON and lamp-OFF messages to the instrument cluster. If the part time indicator fails to light during the actuator test, replace the bulb with a
known good unit. For further diagnosis of the part time indicator or the instrument cluster circuitry that controls the indicator, refer to Instrument
Cluster Diagnosis and Testing. For proper diagnosis of the transfer case switch, the PCM, the PCI data bus, or the electronic message inputs to the
instrument cluster that control the part time indicator, a DRB III scan tool is required. Refer to the appropriate diagnostic information.
TRANS RANGE INDICATOR ILLUMINATION
The Transmission Range Indicator Lamp, mounted on the floor console, uses electroluminescent technology as the light source. This lamp requires a
120 volt AC signal that is provided by a power converter included as part of the assembly. The module is not serviceable separately Because of a
potential shock hazard, diagnostic testing of the lamp assembly should be avoided Refer to TRANSMISSION, Range Selector Assembly REMOVAL
and INSTALLATION.
