Rear Wiper Motor: Operation

The rear wiper motor operation is controlled by the Body Control Module (BCM), which uses a 20 amp fuse and a relay which are both located in the Power Distribution Center (PDC) to control rear wiper system operation for energizing or de-energizing the rear wiper motor. The BCM uses internal programming, hardwired inputs received from the right (wiper) multifunction switch and the rear wiper motor park switch as well as electronic messages received over the Controller Area Network (CAN) data bus to provide the rear wiper and washer system operating modes.

The rear wiper motor park switch is a single pole, single throw, momentary switch within the wiper motor that is mechanically actuated by the wiper motor transmission components. The park switch alternately closes and opens a voltage signal for the rear wiper motor electronic control logic circuitry of the BCM. The park switch is normally an open circuit when the rear wiper blade is in the parked position, and is connected to fused ignition output when the rear wiper blade is anywhere except parked.

This park switch input allows the electronic logic circuits of the BCM to control all of the electronic features of rear wiper motor operation and to keep the motor energized long enough to complete its current wipe cycle and park the wiper blade at the base of the glass after the status of the rear wiper system or the ignition switch transitions to OFF. The internal BCM circuitry pulls the park switch sense input to ground when the switch is open so that the microcontroller sees a ground when the wiper blade is parked.

The rear wiper motor is grounded at all times through a take out with an eyelet terminal connector in the body wire harness that is secured to a ground location in the passenger compartment. The automatic resetting circuit breaker protects the motor from overloads. The rear wiper motor transmission converts the rotary output of the wiper motor to the back and forth wiping motion of the rear wiper arm and blade on the left rear door glass.

The hardwired inputs and outputs of the rear wiper motor may be diagnosed using conventional diagnostic tools and procedures. Refer to the appropriate wiring information. However, conventional diagnostic methods will not prove conclusive in the diagnosis of the rear wiper motor or the electronic controls and communication between other modules and devices that provide some features of the rear wiper and washer system. The most reliable, efficient and accurate means to diagnose the rear wiper motor or the electronic controls and communication related to rear wiper motor operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.