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 and rear wiper and washer system functions with the control knob (1) and control sleeve (2) 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 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 front wiper system operating modes. In the DELAY mode, the control knob also allows the vehicle operator to select from one of four intermittent wipe DELAY intervals. In the AUTO mode, the control knob allows the vehicle operator to select from one of four automatic wiper sensitivity levels.

Depressing the control knob towards the steering column actuates the momentary front washer system switch, which selects the WASH and WIPE-AFTER-WASH modes depending upon when and how long the switch is held closed. Rotating the control knob downward actuates another 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 control knob is released.

The multi-function switch provides hard wired analog and resistor multiplexed inputs to the Steering Control Module (SCM) internal to the Steering Column Control Module (SCCM) for all of the wiper and washer system functions. The SCM then sends electronic wiper switch and washer switch status messages to the Totally Integrated Power Module (TIPM) over the Controller Area Network (CAN) data bus requesting the appropriate wiper and washer system operating modes.

Front wiper and washer system operation is completely controlled by the SCM and TIPM logic circuits, and that logic will only allow these systems to operate when the ignition switch is in the ACCESSORY or ON positions. The TIPM uses intelligent, high current, self-protected high side switches to control integrated wiper relays that control wiper system operation by energizing or de-energizing the wiper motor low and high speed brushes. The TIPM 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.

AUTOMATIC WIPE MODE

If the vehicle is equipped with the optional automatic wiper system and it is enabled, when the control knob on the control stalk of the multi-function switch is moved to one of the four sensitivity positions, the SCM sends an electronic wiper switch sensitivity message to the TIPM and the Wireless Ignition Node (WIN) (also sometimes referred to as the Wireless Control Module/WCM or Sentry Key REmote Entry Module/SKREEM) over the CAN data bus. The WIN, which is a Local Interface Network (LIN) data bus master, relays the wiper switch sensitivity message to the Light Rain Sensor Module (LRSM) (also known as the Light Sensor Module/LSM or Rain Sensor Module/RSM), which is a LIN slave, over the LIN data bus.

The LRSM monitors an area within the wipe pattern of the windshield glass for the accumulation of moisture. Based upon internal programming and the selected sensitivity level, when sufficient moisture has accumulated the LRSM sends the appropriate electronic wipe command messages back to the WIN over the LIN data bus. The WIN relays the wipe command messages to the TIPM over the CAN data bus, then the TIPM operates the front wiper system accordingly.

As the sensitivity level is set higher, the LRSM is more sensitive to moisture accumulation and will send wipe commands more frequently. The third (middle) sensitivity position of the control knob is designed to provide optimal wiper performance for most typical driving requirements. The TIPM logic is also programmed to provide an immediate wipe cycle each time the control knob on the control stalk of the multi-function switch is moved from the OFF position to one of the four sensitivity positions, and another immediate wipe cycle each time the control knob is moved from a lower sensitivity position to a higher sensitivity position.

Also, if a vehicle is equipped with automatic wipers but the feature has been disabled using the customer programmable features function, when any sensitivity position is selected with the control knob the system will respond in the same manner as in the intermittent wipe mode. The automatic wiper system also has features designed to protect the mechanical components of the wiper system, and will not allow automatic wiper operation under the following conditions:

- Low Ambient Temperature - When the ambient temperature is below 0° C (32° F), the automatic wipers will not operate during a new ignition cycle until the wiper switch has been moved to a different position than that which was selected at the moment the current ignition cycle began, or until a vehicle speed input is detected.
- Transmission In Neutral - When the transmission gear selector is placed in the NEUTRAL position with the ignition switch in the ON position, the automatic wipers will not operate during the current ignition cycle until the wiper switch has been moved to a different position than that which was selected at the moment the NEUTRAL position was selected, until the vehicle speed is greater than 8 kilometers-per-hour (5 miles-per-hour) or until the transmission gear selector is moved out of the NEUTRAL position, whichever occurs first.

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 TIPM over the CAN data bus. The TIPM 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 TIPM. The TIPM 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 TIPM, 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 TIPM. The TIPM 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 TIPM 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 TIPM is again closed to ground.

HEADLAMPS ON WITH WIPERS MODE

The circuitry of the EMIC provides an automatic HEADLAMPS ON WITH WIPERS mode for vehicles equipped with the optional automatic headlamps. This is a customer programmable feature that can be enabled or disabled through the Electronic Vehicle Information Center (EVIC). If this feature is enabled, when the headlamp switch is in the AUTO position, the headlamps will turn ON automatically whenever the windshield wipers are turned ON; and, if the headlamps were turned ON automatically when the wipers were turned ON, they will also turn OFF automatically when the wipers are turned OFF.

If this feature is enabled in vehicles equipped with the optional automatic wiper feature, when the automatic wiper mode is selected the headlamps will turn ON automatically only after the wipers complete three automatic wipe cycles within about 30 seconds, and they will turn OFF automatically after 3 minutes elapse without any automatic wipe cycles unless ambient light conditions dictate otherwise.

INTERMITTENT WIPE MODE

The following applies to vehicles not equipped with the optional automatic wiper system, or to vehicles equipped with the automatic wiper system that have been disabled using the customer programmable features function.

When the control knob on the control stalk of the multi-function switch is moved to one of the four DELAY interval positions the SCM sends an electronic wiper switch delay interval status message to the TIPM. Then the TIPM electronic intermittent wipe logic circuit responds by calculating the correct length of time between wiper sweeps based upon the selected delay interval input.

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

The TIPM logic is also programmed to provide vehicle speed sensitivity to the selected intermittent wipe delay intervals. In order to provide this feature, the TIPM 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 TIPM. The TIPM then 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 TIPM 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 TIPM. Then the TIPM 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 (or sensitivity level with automatic wipers) positions, the washer pump/motor operation is the same. However, the TIPM logic also overrides the selected delay interval or sensitivity level 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 or sensitivity level several wipe cycles after the control knob is released. If the WASH switch is held closed for more than about 10 seconds, the TIPM will suspend washer pump/motor operation until the control knob is released for about 2 seconds, 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 TIPM. Then the TIPM directs battery current and ground to operate the washer pump/motor in the front wash direction and energizes the front 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 TIPM 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 TIPM will suspend washer pump/motor operation until the knob 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 TIPM monitors the changing state of the wiper motor park switch through a hard wired wiper park switch sense circuit input. This input allows the TIPM 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.