Rear

REAR





The rear wiper and washer system is designed to provide the vehicle operator with a convenient, safe, and reliable means of maintaining visibility through the liftgate glass. The various components of this system are designed to convert electrical energy produced by the vehicle electrical system into the mechanical action of the wiper blade to wipe the outside surface of the glass, as well as into the hydraulic action of the washer system to apply washer fluid stored in an on-board reservoir to the area of the glass to be wiped. When combined, these components provide the means to effectively maintain clear visibility for the vehicle operator by removing excess accumulations of rain, snow, bugs, mud, or other minor debris from the outside liftgate glass surface that might be encountered while driving under numerous types of inclement operating conditions.

The vehicle operator initiates all rear wiper and washer system functions with the control knob (1) of the rear wiper and washer switch located in a corner of the heater-air conditioner control (2), just below the radio on the instrument panel. Rotating the control knob (1) to a detent position selects the rear wiper system operating mode, either continuous or intermittent. Intermittent operation provides one of four fixed delay intervals, from 5 to 21 seconds. Depressing the control knob activates the rear washer system.

When a rear wiper or washer switch mode is selected, the circuitry within the heater-air conditioner control sends an electronic rear wiper/washer switch status message over the Controller Area Network (CAN) data bus to the Front Control Module (FCM) indicating the selected rear wiper and washer system operating mode. The FCM provides the necessary outputs to operate the washer pump/motor unit and the rear wiper relay, which provides battery voltage to operate the rear wiper motor.

The hard wired circuits and components of the rear wiper and washer system 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 and washer system 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 and washer system or the electronic controls and communication related to rear wiper and washer system operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.

OPERATING MODES

Following are paragraphs that briefly describe the operation of each of the rear wiper and washer system operating modes.

CONTINUOUS WIPE MODE

When the ON position of the rear wiper/washer control knob is selected the heater-air conditioner control sends an electronic wiper switch status message to the FCM, then the FCM energizes the rear wiper relay control coil. This directs battery current through the relay contacts to the rear wiper motor, causing the wiper to cycle continuously at a fixed speed until the FCM de-energizes the rear wiper relay.

INTERMITTENT WIPE MODE

When the rear wiper/washer control knob is moved to one of the DELAY interval positions the heater-air conditioner control sends an electronic wiper switch delay status message to the FCM, then the FCM electronic intermittent wipe logic circuit responds by calculating the correct length of time between wiper sweeps based upon the selected DELAY interval input. The FCM monitors the changing state of the rear wiper motor park switch through a hard wired park switch sense input. This input allows the FCM to determine the proper intervals at which to energize and de-energize the rear wiper relay to operate the wiper motor intermittently for one cycle at a time.

WASH MODE

When the rear wiper/washer control knob is depressed to the momentary WASH position, the heater-air conditioner control sends an electronic washer switch status message to the FCM, then the FCM directs battery current and ground to the washer pump/motor unit. This will cause the washer pump/motor unit to be energized for as long as the WASH switch is held closed (up to about 30 seconds) and to be de-energize when the rear wiper/washer control knob is released.

WIPE-AFTER-WASH MODE

When the rear wiper/washer control knob is released from the momentary WASH position, the heater-air conditioner control sends an electronic washer switch status message to the FCM. The FCM de-energizes the washer pump/motor, but allows the rear wiper motor to operate for several wipe cycles before it de-energizes the rear wiper relay.

OFF MODE

When the OFF position of the rear wiper/washer control knob is selected, the heater-air conditioner control sends an electronic washer switch status message to the FCM. Then, one of three events is possible. The event that will occur depends upon the position of the wiper blade on the liftgate glass and the mode the wiper motor is operating under at the moment that the OFF position is selected. If the wiper blade is in the down position on the glass and the rear wiper system is operating in the fixed or fixed intermittent cycle modes when the OFF position is selected, the park switch is open and the FCM de-energizes the rear wiper relay control coil causing the rear wiper motor to cease operation.

If the wiper blade is not in the down position on the glass and is operating in the fixed or fixed intermittent cycle modes when the OFF position is selected, the park switch is closed to ground and the FCM keeps the rear wiper relay control coil energized to operate the rear wiper motor until the rear wiper blade is in the down position on the glass and the park switch input is an open circuit.

The third event occurs with the rear wiper operating in the WIPE-AFTER-WASH mode when the OFF position is selected, in which case the FCM will continue to run the wiper motor until the completion of about three wiper blade sweeps before the rear wiper blade is parked. The FCM will also run the rear wiper motor to park the rear wiper blade if the ignition switch is turned to the OFF position while the rear wiper system is still operating.