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 outer surface of the liftgate glass that might be encountered while driving the vehicle under numerous types of inclement operating conditions.

The vehicle operator initiates all front and rear wiper and washer system functions with the control sleeve (1) on the control stalk (3) of the multi-function switch that extends from the left side of the steering column, just below the steering wheel. Rotating the control sleeve to the OFF or INTERMITTENT detent positions or the momentary WASH position selects the rear wiper and washer system operating modes.

The multi-function switch provides hard wired analog and resistor multiplexed inputs to the Steering Control Module (SCM) integral and internal to the multi-function switch housing for all of the rear wiper and washer system functions. The SCM then sends electronic rear wiper/washer switch status messages to the Steering Angle Sensor (SAS) integral to the clockspring over a Local Interface Network (LIN) data bus. The SCM is a LIN slave node, while the SAS is both a LIN master node and a gateway to the Controller Area Network (CAN) data bus. The SAS responds to the SCM inputs by sending electronic rear wiper/washer switch request messages to the Body Control Module (BCM) (also known as the Common Body Controller/CBC) over the CAN data bus requesting the appropriate rear wiper and washer system operating modes.

Rear wiper and washer system operation are completely controlled by the SCM, SAS and BCM logic circuits, and that logic will only allow these systems to operate when the ignition switch is in the ACCESSORY or ON positions. The BCM uses intelligent, high current, self-protected high side and low side drivers to control rear wiper system operation by energizing or de-energizing the rear wiper motor. The BCM uses an H-bridge circuit to control the operation of the reversible washer pump/motor unit. The multi-function switch circuitry receives a clean ground output from the SCM on a multi-function switch return circuit, then provides analog and multiplexed inputs to the SCM to indicate the selected rear wiper and rear washer system mode.

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 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.

INTERMITTENT WIPE MODE

When the INTERMITTENT WIPE position of the control sleeve on the control stalk of the multi-function switch is selected, the SCM sends an electronic rear wiper switch status message to the SAS over the LIN data bus, then the SAS relays an electronic rear wiper switch request message to the BCM over the CAN data bus, and the BCM directs battery current to the rear wiper motor at fixed delay intervals to enable the rear wiper motor intermittent wipe mode.

WASH MODE

When the control sleeve of the multi-function switch is rotated to the momentary rear WASH position, the SCM sends an electronic rear washer switch status message to the SAS over the LIN data bus, then the SAS relays an electronic rear washer switch request message to the BCM over the CAN data bus, then the BCM directs battery current to the rear wiper motor and directs battery current and ground to the washer pump/motor unit. These outputs will cause the washer pump motor and the rear wiper motor to operate continuously for as long as the switch is held closed up to approximately 10 seconds. The washer pump is de-energized as soon as the control sleeve is released, but the rear wiper motor continues to operate for two to three continuous cycles before reverting to the fixed delay interval operation. The BCM uses a hard wired output from a park switch internal to the rear wiper motor as an additional logic input to monitor the position of the rear wiper blade on the glass and to control the number of continuous wiper sweeps following washer operation.