Rear Wiper And Washer System: 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 flip-up 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 flip-up 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 stalk (1) of the right (wiper) multi-function switch that extends from the right side of the steering column, just below the steering wheel. Rotating the control sleeve (3) on the control stalk to the OFF or INTERMITTENT detent positions or the momentary WASH position selects the rear wiper and washer system operating modes.
The right multi-function switch provides hard wired analog and resistor multiplexed inputs to the Steering Control Module (SCM) integral to the left (lighting) multi-function switch for all of the rear wiper and washer system functions. The SCM then sends electronic rear wiper/washer switch status messages to the ElectroMechanical Instrument Cluster (EMIC) (also known as the Cab Compartment Node/CCN) over a Local Interface Network (LIN) data bus. The EMIC then sends electronic rear wiper/washer switch request messages to the Front Control Module (FCM) over the Controller Area Network (CAN) data bus requesting the appropriate rear wiper and washer system operating modes.
The FCM provides battery voltage and ground to operate the washer pump/motor unit and a control output to the rear wiper relay, which provides battery voltage to operate the rear wiper module for as long as the ignition switch is in the ACCESSORY or ON positions, plus a delay after the ignition switch is turned to any other position long enough to allow the rear wiper module to park the rear wiper blade off of the liftgate flip-up glass. The FCM provides hard wired signal outputs to the rear wiper module on two circuits that indicate the selected operating mode and delay interval that the rear wiper module uses to control rear wiper motor operation.
Rear wiper and washer system operation is completely controlled by the SCM, EMIC and FCM logic circuits, and that logic will only allow these systems to operate when the ignition switch is in the ACCESSORY or ON positions. Battery current is directed from the Integrated Power Module (IPM) to the rear wiper relay in the Junction Block (JB) through a fused B(+) circuit. The FCM uses an H-bridge circuit to control the operation of the reversible washer pump/motor unit. The right multi-function switch circuitry receives a clean ground output from the SCM on a multi-function switch return circuit, then provides analog and resistor 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 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.