Cherokee 4WD LHD L6-4.0L VIN S (2001)
Cruise Control Indicator Lamp: Description and Operation
A cruise indicator lamp is standard equipment on all instrument clusters, but is only functional on vehicles equipped with the optional speed control
system. The cruise indicator lamp is located near the upper edge of the instrument cluster overlay, in the upper left quadrant of the cluster. The cruise
indicator lamp consists of a stenciled cutout of the word "CRUISE" in the opaque layer of the instrument cluster overlay. The dark outer layer of the
overlay prevents the indicator from being clearly visible when the lamp is not illuminated. A green lens behind the cutout in the the opaque layer of the
overlay causes the "CRUISE" text to appear in green through the translucent outer layer of the overlay when it is illuminated from behind by a
replaceable incandescent bulb and bulb holder unit located on the instrument cluster electronic circuit board. The cruise indicator lamp is serviced as a
unit with the instrument cluster.
The cruise indicator lamp gives an indication to the vehicle operator when the speed control system is turned ON, regardless of whether the speed control
is engaged. This lamp is controlled by the instrument cluster circuit board based upon the cluster programming and electronic messages received by the
cluster from the Powertrain Control Module (PCM) over the Chrysler Collision Detection (CCD) data bus. The cruise indicator lamp bulb receives
battery current on the instrument cluster electronic circuit board through the fused ignition switch output (st-run) circuit whenever the ignition switch is
in the ON or Start positions; therefore, the lamp will always be OFF when the ignition switch is in any position except ON or Start. The lamp bulb only
illuminates when it is switched to ground by the instrument cluster circuitry. The instrument cluster will turn ON the cruise indicator lamp for the
following reasons:
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Cruise Lamp-ON Message - Each time the cluster receives a cruise lamp-ON message from the PCM indicating the speed control system has been
turned ON. The lamp remains illuminated until the cluster receives a cruise lamp-OFF message from the PCM or until the ignition switch is turned
to the OFF position, whichever occurs first.
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Actuator Test - Each time the cluster is put through the actuator test, the lamp will be turned ON and OFF in a prescribed sequence to confirm the
functionality of the lamp and the cluster circuitry.
The PCM continually monitors the speed control switches to determine the proper outputs to the speed control servo. The PCM then sends the proper
cruise indicator lamp messages to the instrument cluster. If the cruise indicator fails to light when the speed control system is turned ON, replace the bulb
with a known good unit. For further diagnosis of the cruise indicator lamp or the instrument cluster circuitry that controls the lamp, (Refer to
INSTRUMENT CLUSTER - DIAGNOSIS AND TESTING). For proper diagnosis of the speed control system, the CCD data bus, or the message inputs
to the instrument cluster that control the cruise indicator, a DRB III scan tool and the appropriate diagnostic information are required.