Front

FRONT




Front Wipers Only

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




Front and Rear Wipers

Two front wiper systems are available: The standard intermittent wipe system, or an optional automatic wipe system. The vehicle operator initiates all front and optional rear wiper and washer system functions using the controls on the end of the multi-function switch control stalk that extends from the left right side of the steering column, just below the steering wheel. Rotating the control knob (1) on the end of the control stalk to the positions marked on the fixed band (2) on the stalk selects the 0 (Off), I (Intermittent - without the optional rain/light sensor) or (Automatic - with the optional rain/light sensor), II (Low), or III (High) front wiper system operating modes. Pushing the knob on the end of the control stalk towards the steering column up to the actuation point activates the front wiper pulse wipe mode without washer fluid, while pushing the knob beyond the actuation point activates the front wiper system in combination with dispensing washer fluid onto the windshield glass.

Front wiper and washer system operation is completely controlled by the Body Control Module (BCM) (also known as the Signal Acquisition and Actuation Module/SAM) logic circuits based upon electronic wipe command and wash commandmessage inputs received from the Steering Control Module (SCM) (also known as the steering column module/MRM) based upon the selected multi-function switch position and, on vehicles so equipped, from the Roof Control Module (RCM) (also known as the Overhead Control Panel/OCP control unit or DBE) based upon inputs received from the rain/light sensor. The BCM will only allow these systems to operate when the ignition switch is in the ON position. The BCM uses high side drivers to control wiper system operation by energizing or de-energizing the front wiper on-off and high-low relays, and a low side driver to control the front washer pump/motor unit.

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 front wiper and washer system or 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, the rain/light sensor monitors an area within the wipe pattern of the windshield glass for the accumulation of moisture whenever the ignition switch is in the ON position. The RCM continually monitors the output of the rain/light sensor and sends the appropriate wipe command messages to the BCM. Depending upon the intensity of the precipitation monitored by the rain/light sensor, the front wiper system will be automatically operated in intermittent, continuous low or continuous high speed mode. When the control knob on the control stalk of the multi-function switch is moved to the I (Automatic) position, the SCM monitors this selection and sends an electronic wiper switch automatic message to the BCM. Based upon internal programming, the BCM operates the front wiper system accordingly.

The BCM logic is also programmed to provide an immediate initialization wipe cycle each time the control knob on the control stalk of the multi-function switch is moved from the 0 (Off) position to the I position while the ignition switch is in the ON position. This initialization wipe cycle is intended to clear the area of the windshield monitored by the rain/light sensor of moisture, dirt or debris to ensure accurate readings from the sensor. If the I position of the multi-function switch is already selected when the ignition switch is turned to the ON position, the initialization wipe cycle will not occur and the multi-function switch must be cycled manually to clear the glass over the sensor. Also, when the I position is selected with the multi-function switch but the automatic wipe feature has been disabled due to an ineffective circuit or component, the system will respond in the same manner as in the intermittent wipe mode on vehicles without the rain/light sensor.

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 certain conditions. If the monitored ambient temperature is below 4° C (39° F) at the beginning of a new ignition cycle, the automatic wipers will not operate until the multi-function switch has been cycled, until a vehicle speed input greater than zero is detected, or until the monitored ambient temperature rises above 4° C (39° F).

The BCM logic is programmed to provide vehicle speed sensitivity to the automatic wipe mode. In order to provide this feature the BCM monitors electronic vehicle speed messages from the Antilock Brake System (ABS) module (also known as the Controller Antilock Brake/CAB, the Electronic Stability Program/ESP module, the ESP_SBC, or the ESP8) and automatically increases the intermittent delay interval, reduces the continuous wiper operating speed from high to low speed or from low to intermittent whenever the vehicle speed drops below about 5 kilometers-per-hour (3 miles-per-hour). The wiper speed automatically returns to the previous intervals or speed when the vehicle speed exceeds about 8 kilometers-per-hour (5 miles-per-hour).

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 has been disabled due to an ineffective circuit or component. When the control knob on the control stalk of the multi-function switch is moved to the I (Intermittent) position, the SCM monitors this selection and sends an electronic wiper switch intermittent status message to the BCM. Then the BCM electronic intermittent wipe logic circuit responds by calculating the correct length of time between wiper sweeps.

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 front wiper on-off relay to operate the wiper motor intermittently for one low speed cycle at a time. The interval between wipes is about six seconds.

The BCM logic is also programmed to provide vehicle speed sensitivity to the intermittent wipe delay interval. In order to provide this feature the BCM monitors electronic vehicle speed messages from the ABS module and increases the delay interval to about 9 seconds whenever the vehicle speed drops below about 5 kilometers-per-hour (3 miles-per-hour). The interval returns to about 6 seconds when the vehicle speed exceeds about 8 kilometers-per-hour (5 miles-per-hour).

CONTINUOUS WIPE MODE

When the II (Low) position of the control knob on the control stalk of the multi-function switch is selected, the SCM monitors this selection and sends an electronic wiper switch low status message to the BCM, then the BCM energizes the front wiper on-off relay. This directs battery current through the contacts of the front wiper high-low relay to the low speed brush of the wiper motor, causing the wipers to cycle at low speed.

When the III (High) position of the control knob is selected, the SCM sends an electronic wiper switch high status message to the BCM, then the BCM energizes the front wiper on-off and high-low relays. This directs battery current through the contacts of the both relays to the high speed brush of the wiper motor, causing the wipers to cycle at high speed.

When the 0 (Off) position of the multi-function switch control knob is selected, the SCM monitors this selection and sends an electronic wiper switch off status message to the BCM. If the wiper motor was operating at high speed, the BCM immediately de-energizes the front wiper high-low relay causing the wiper motor to return to low speed operation. 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 0 position is selected.

If the wiper blades are in the down position on the windshield when the 0 position is selected, the park switch that is integral to the wiper motor is closed to ground and provides a hard wired park switch sense input to the BCM. The BCM then de-energizes the front wiper on-off relay and the wiper motor ceases to operate. If the wiper blades are not in the down position on the windshield at the moment the 0 position is selected, the park switch is an open circuit and the BCM keeps the front wiper on-off relay energized, which causes the wiper motor to continue running 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.

PULSE WIPE MODE

When the end of the control knob on the control stalk of the multi-function switch is depressed momentarily toward the steering column to the actuation point, the SCM monitors this selection and sends an electronic wiper switch pulse status message to the BCM. Then the BCM energizes the front wiper on-off relay without energizing the front washer pump/motor for as long as the switch is held in this position, then de-energizes the relay when the switch is released, 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 in this momentary position.

WASH MODE

When the end of the control knob on the control stalk of the multi-function switch is depressed momentarily toward the steering column beyond the actuation point, the SCM monitors this selection and sends an electronic washer switch status message to the BCM. The BCM then energizes the washer pump/motor unit and the wiper motor at low speed for as long as the switch is held and de-energizes the pump when the control knob is released.

If the control knob is held depressed less than about 1 second, the BCM will add one additional low speed wipe cycle after the switch is released before it de-energizes the front wiper on-off relay and parks the wiper blades near the base of the windshield. If the control knob is held depressed greater than about 1 second, the BCM will add three additional low speed wipe cycles after the switch is released before it de-energizes the front wiper on-off relay and parks the wiper blades near the base of the windshield. 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 switch is released