Motor-Rear Window Wiper: Operation

The rear wiper motor operation is controlled by the rear wiper relay, which controls battery current flow to the rear wiper motor 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 Steering Control Module (SCM) to determine when to energize or de-energize the rear wiper relay.

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 monitor whether the glass is opened or closed, and two hard wired signal inputs from the SCM indicating the mode selected with the rear wiper switch circuitry of the right (wiper) multi-function switch. 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 methods. Refer to the appropriate wiring information. However, conventional diagnostic methods may not prove conclusive in the diagnosis of the SCM, the FCM, the CAN data bus or the electronic message inputs used to control rear wiper motor operation. The most reliable, efficient, and accurate means to diagnose the SCM, the FCM, the CAN data bus and the electronic message inputs and outputs that control rear wiper motor operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.