Section 1633 (Wiper System & Washer System - (Service Information) - 2500 Hd): Operation: Notes
The wiper and washer system is designed to provide the vehicle operator with a convenient, safe and reliable means of maintaining visibility through the windshield 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 blades 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 windshield glass surface that might be encountered while driving the vehicle under numerous types of inclement operating conditions.
The vehicle operator initiates all wiper and washer system functions with the control knob (1) on the end of the control stalk (2) of the multifunction switch that extends from the left side of the steering column, just below the steering wheel. Rotating the control knob on the end of the control stalk, selects the OFF, DELAY (except with the optional automatic wiper system), AUTO (with the optional automatic wiper system only), LOW or HIGH wiper system operating modes. In the DELAY mode, the control knob also allows the vehicle operator to select from one of five intermittent wipe delay intervals. In the AUTO mode, the control knob allows the vehicle operator to select from one of five automatic wiper sensitivity levels.
Pressing the control knob towards the steering column to the first detent actuates a momentary switch and selects the MIST mode, which cycles the wiper blades for as long as the switch is held closed then completes the current cycle and parks the blades at the base of the windshield after the switch is released. Pressing the control knob to the second detent actuates the momentary washer system switch, which selects the Wash or Wipe-After-Wash modes depending upon when and how long the switch is held closed.
The multifunction switch provides hard wired analog and resistor multiplexed inputs to the Steering Control Module (SCM) internal and integral to the multifunction switch housing for all of the wiper and washer system functions. The SCM then sends electronic wiper and 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 wiper system and washer system request messages to the Body Control Module (BCM) over the CAN data bus requesting the appropriate wiper and washer system operating modes.
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 status of the ignition switch (Keyless Ignition Node/KIN or IGnition Node Module/IGNM) is ACCESSORY or ON. The BCM uses high side drivers to control the solid state wiper ON/OFF and HIGH/LOW relays soldered onto the Power Distribution Center (PDC) Printed Circuit Board (PCB), which controls wiper system operation by directing battery current to the proper wiper motor low or high speed brushes. The BCM uses a high side driver to control the operation of the washer pump/motor unit. The multifunction switch circuitry receives battery current and a clean ground output from the SCM, then provides analog and multiplexed inputs to the SCM to indicate the selected wiper and washer system mode.
The hard wired circuits and components of the 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 wiper and washer system or the electronic controls and communication between other modules and devices that provide some features of the wiper and washer system. The most reliable, efficient and accurate means to diagnose the wiper and washer system or the electronic controls and communication related to wiper and washer system operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.