Motor, Wiper: Operation: Rear
The rear wiper motor operation is controlled by the Body Control Module (BCM) which uses low side drivers to control a rear wiper motor relay integral to the Printed Circuit Board (PCB) within the Power Distribution Center (PDC), which controls rear wiper system operation for energizing or de-energizing the rear wiper motor. The BCM uses internal programming and electronic messages received over the Controller Area Network (CAN) data bus from the Steering Column Control Module (SCCM) microcontroller to provide the appropriate rear wiper and washer system operating modes. The SCCM microcontroller uses hard wired analog and digital inputs from the multifunction switch to determine when to send electronic rear wiper system requests to the BCM.
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 BCM microcontroller also receives an external control input from the liftgate ajar switch sense circuit. If the BCM senses that the liftgate is ajar, it will not allow the rear wiper motor to operate. Also, if the BCM rear wiper logic monitors a request for the liftgate to be opened while the rear wiper is running, the BCM will keep the motor energized long enough to complete its current wipe cycle and park the wiper blade at the base of the glass. The rear wiper function of the multifunction switch will then have to be cycled Off, then back On to resume rear wiper motor operation after the liftgate is closed.
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 the body sheet metal. The automatic resetting circuit breaker and the integral clutch mechanism protect 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 liftgate glass.
The hard wired 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.