Front

FRONT





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

The vehicle operator initiates all front wiper and washer system functions with the control knob (1) on the end of 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 knob on the end of the control stalk, selects the OFF, DELAY, LOW, or HIGH front 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.

Depressing 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. Depressing 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 multi-function switch provides hard wired analog and resistor multiplexed inputs to the Steering Control Module (SCM) internal and integral to the multi-function 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 and washer system request messages to the Body Control Module (BCM) (also known as the Common Body Controller/CBC) over the CAN data bus requesting the appropriate wiper and washer system operating modes.

Front 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 the solid state wiper on/off and high/low relays on the BCM printed circuit board, which controls wiper system operation by directing battery current to the proper front wiper motor low or high speed brushes. The BCM uses an H-bridge circuit to control the operation of the reversible washer pump/motor unit. The multi-function 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 front wiper and front washer system mode.

The hard wired circuits and components of the front 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 front wiper and washer system. The most reliable, efficient, and accurate means to diagnose the front wiper and washer system or the electronic controls and communication related to front 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 front wiper and washer system operating modes.

CONTINUOUS WIPE MODE

When the LOW position of the control knob on the control stalk of the multi-function switch is selected the SCM sends an electronic wiper switch low status message to the SAS over the LIN data bus. The SAS then relays an electronic wiper switch low request message to the BCM over the CAN data bus. The BCM then directs battery current to the low speed brush of the wiper motor, causing the wipers to cycle at low speed.

When the HIGH position of the control knob is selected, the SCM sends an electronic wiper switch high status message to the SAS. The SAS then relays an electronic wiper switch high request message to the BCM. The BCM then directs battery current to the high speed brush of the wiper motor, causing the wipers to cycle at high speed.

When the OFF position of the multi-function switch control knob is selected, the SCM sends an electronic wiper switch off status message to the SAS, the SAS relays an electronic wiper switch off request message to the BCM, then one of two events will occur. The event that occurs depends upon the position of the wiper blades on the windshield at the moment that the control knob OFF position is selected.

If the wiper blades are in the down position on the windshield when the OFF position is selected, the park switch that is integral to the wiper motor is closed to ground, which provides a hard wired park switch sense input to the BCM. The BCM then de-energizes the wiper motor and the wiper motor ceases to operate. If the wiper blades are not in the down position on the windshield at the moment the OFF position is selected, the park switch is an open circuit and the BCM continues running the wiper motor at low speed until the wiper blades are in the down position on the windshield and the park switch input to the BCM is again closed to ground.

INTERMITTENT WIPE MODE

When the control knob on the control stalk of the multi-function switch is moved to one of the five DELAY interval positions the SCM sends an electronic wiper switch delay interval status message to the SAS. The SAS then relays an electronic wiper switch delay interval request message to the BCM. The BCM's electronic intermittent wipe logic circuit responds by calculating the correct length of time between wiper sweeps based upon the selected delay interval input.

The BCM monitors the changing state of the wiper motor park switch through a hard wired park switch sense input. This input allows the BCM to determine the proper intervals at which to energize and de-energize the wiper motor intermittently for one low speed cycle at a time.

The BCM logic is also programmed to provide vehicle speed sensitivity to the selected intermittent wipe delay intervals. In order to provide this feature, the BCM monitors electronic vehicle speed messages from the Controller Antilock Brake (CAB) and doubles the selected delay interval whenever the vehicle speed is about 16 kilometers-per-hour (10 miles-per-hour) or less.

MIST WIPE MODE

When the control knob of the multi-function switch is rotated downward to the momentary MIST position, the SCM sends an electronic wiper mist mode status message to the SAS, the SAS relays an electronic wiper mist mode request message to the BCM, then the BCM energizes the low speed brush of the wiper motor for as long as the switch is held closed, then de-energizes the motor when the state of the switch changes to open, parking the wiper blades near the base of the windshield. The BCM can operate the front wiper motor in this mode for only one low speed cycle at a time, or for an indefinite number of sequential low speed cycles, depending upon how long the switch is held closed.

WASH MODE

When the control knob of the multi-function switch is depressed toward the steering column to the momentary front WASH position for more than about one-half second with the wiper system operating, the SCM sends an electronic washer switch status message to the SAS, the SAS relays an electronic washer switch request message to the BCM. Then the BCM directs battery current and ground to the washer pump/motor. This will cause the washer pump/motor to be energized in the front wash direction for as long as the switch is held closed (up to approximately 10 seconds) and to be de-energized when the control knob is released.

When the control knob is depressed to the momentary front WASH position while the front wiper system is operating in one of the DELAY interval positions, the washer pump/motor operation is the same. However, the BCM logic also overrides the selected delay interval and operates the front wiper motor in a continuous low speed mode for as long as the control knob is held in the front momentary WASH position, then reverts to the selected delay interval several wipe cycles after the control knob is released. If the WASH switch is held closed for more than approximately 10 seconds, the BCM will suspend washer pump/motor operation until the control stalk is released for about 2 seconds and then cycled back to the WASH position.

WIPE-AFTER-WASH MODE

When the control knob of the multi-function switch is depressed toward the steering column to the momentary front WASH position for more than about one-half second while the wiper system is not operating, the SCM sends an electronic washer switch status message to the SAS. Then the SAS relays an electronic washer switch request message to the BCM, and the BCM directs battery current and ground to the washer pump/motor and energizes the wiper motor in a continuous low speed mode for as long as the switch is held closed (up to approximately 10 seconds). When the control knob is released, the BCM de-energizes the washer pump/motor immediately, but allows the wiper motor to operate for two or three additional wipe cycles before it de-energizes the wiper motor and parks the wiper blades near the base of the windshield.

If the control knob is held inward for more than about 10 seconds, the BCM will suspend washer pump/motor operation until the stalk is released for about 2 seconds and then cycled back to the WASH position; however, the wipers will continue to operate for as long as the switch is held closed. The BCM monitors the changing state of the wiper motor park switch through a hard wired wiper park switch sense circuit input. This input allows the BCM to count the number of wipe cycles that occur after the control knob is released, and to determine the proper interval at which to de-energize the wiper motor to complete the WIPE-AFTER-WASH mode cycle.