Section 9 (Wiper System & Washer System (Service Information)): Operation: Rear: Notes
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 multifunction 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 multifunction switch provides hard wired analog and resistor multiplexed inputs to the Steering Control Module (SCM) integral and internal to the multifunction 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 status is Accessory or On. 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 multifunction switch circuitry receives a clean ground output from the SCM on a multifunction 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.