Wiper Motor - Operation

REAR

The rear wiper relay controls battery current flow to the rear wiper module logic circuit based upon control outputs from the Front Control Module (FCM). The FCM uses internal programming and electronic messages received over the Controller Area Network (CAN) data bus from the Electro Mechanical Instrument Cluster (EMIC) (also known as the Cab Compartment Node/CCN) to determine when to energize or de-energize the rear wiper relay and to determine the selected rear wiper operating mode. The FCM provides hard wired signal outputs to the rear wiper module on two circuits that indicate the selected operating mode and delay interval, which the rear wiper module uses as logic inputs to control rear wiper motor operation.

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 path to ground for the rear wiper motor control circuit input to the wiper motor electronic controls, depending upon the position of the rear wiper blade on the liftgate glass.

The motor control electronics also monitor a hard wired input from the liftgate flip-up glass ajar switch to determine whether the glass is opened or closed. These inputs allow the electronic logic circuits 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 after the wiper system or the ignition switch has been turned OFF, or when the liftgate flip-up glass has been opened.

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 liftgate flip-up 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 or 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.