Grand Cherokee 2WD Limited V8-4.7L (2002)
system is only active when the ignition is in the run/acc position.
The BCM controls the front wiper system with one low-going output to a relay. With this output the BCM determines the motor wipe rate. This
rate is a function of the intermittent wiper switch position and vehicle speed. The BCM times the delay after the wipers have parked. If the driver
goes from a longer to a shorter delay interval, a wipe is done immediately. The speed sensitive delay is set based on the current speed of the
vehicle. If the vehicle crosses above the speed threshold of 10 MPH (16 kmh) while the intermittent wiper delay is occurring, a smaller delay can
be used. If the vehicle crosses below the speed threshold a longer delay should not be used until the current delay is completed.
In the lo-hi and mist state, the BCM constantly outputs an active control signal for a delay of zero. The multifunction switch controls the wiper
high/low relay wiper motor in the hi state. This is done with an additional output from the multifunction switch to a relay which selects the motor
winding to be energized. The BCM does not distinguish between lo-hi-or mist positions. The mist position is a momentary input to the BCM
which causes the wipers to operate at low speed as long as the mist input is present.
The BCM also monitors the front washer motor to perform wipe after wash. The BCM will perform 3 wipes after the wash input is released.
Since the front wiper system is an important safety feature, the BCM will support wiper operation in the event of a failed park input.
If BCM does not detect a change of state on the park input for 8 seconds with the wiper relay energized a Diagnostic Trouble Code will set in the
BCM.
Once a failed park switch is detected, intermittent operation is disabled and the BCM will default to the low speed wiper state when the wiper
switch is in the intermittent position. The wiper relay will be de-energized when the wiper mode switch is in the OFF position. For open and short
states on the wiper mode switch, the wipers should default to OFF.
Rain Sensor Module
The Microprocessor-Based Rain Sensor Module (RSM) senses moisture on the outside of the windshield glass, and sends a wipe command to the
Body Control Module (BCM). The RSM sends a wipe command to the BCM over the PCI data bus. The BCM then activates or deactivates the
front wiper system. Sensitivity inputs are based on the driver-selected settings on the right side multi-function switch.
Speed Sensitive Intermittent Wipe Mode
There are 5 individual delay times with a minimum delay of 1/2 second to a maximum of 18 seconds. When the vehicle speed is under 10 MPH
(16 kmh), the delay time is doubled providing a range of 1 second to 36 seconds.
Mist Wipe
The wiper operates as long as the wiper switch is in the mist position.
Park after Ignition OFF
Because the wiper relays are powered from the battery the BCM can run the wipers to park after the ignition is turned OFF.
Wipe after Wash
When the driver presses the wash button and then releases it, the wiper will continue to run for 3 additional wipe cycles.
The wiper system utilizes the BCM to control the ON/OFF relay for low wiper functions, intermittent wiper delay as the switch position changes,
pulse wipe, wipe after wash mode, and wiper motor park functions. The BCM uses the vehicle speed input to double the usual delay time below 10
MPH (16 kmh).
Front/rear Wiper And Washer Switches (right Multi-function Switch Stalk)
The front windshield and rear liftglass wiper/washer switches are located on the wiper multi-function switch stalk which is secured to the right side
of the multi-function switch mounting housing on the steering column.
A knob on the end of the wiper multifunction switch stalk is rotated to select the desired front wiper speed (HIGH or LOW) or one of the five
intermittent front wiper positions. The wiper stalk is pulled toward the driver to activate the windshield washer system. Both the front wiper and
front washer motors will operate continuously for as long as the stalk is held in the momentary FRONT WASH position.
Another rotary switch on the wiper multifunction switch stalk is rotated to select the desired rear wiper speed (ON or DELAY). The wiper stalk is
pushed toward the instrument panel to activate the rear liftglass washer system. Both the rear wiper and rear washer motors will operate
continuously for as long as the stalk is held in the momentary REAR WASH position.
If any part of the right multi-function switch stalk is faulty or damaged, the entire wiper multi-function switch assembly must be replaced.
