Part 2

CONTINUOUS WIPE MODE
When the LOW position of the control knob on the control stalk of the right (wiper) multi-function switch is selected the SCM sends an electronic wiper switch low message to the FCM, then the FCM energizes the wiper on/off relay. This directs battery current through the normally open contacts of the energized wiper on/off relay and the normally closed contacts of the de-energized wiper high/low relay 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 message to the FCM, then the FCM energizes both the wiper on/off relay and the wiper high/low relay. This directs battery current through the normally open contacts of the energized wiper on/off relay and the normally open contacts of the energized wiper high/low relay 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 message to the FCM. If the wiper motor was operating at high speed, the FCM immediately de-energizes the 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 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 and provides a hard wired park switch sense input to the FCM. The FCM then de-energizes the 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 OFF position is selected, the park switch is an open circuit and the FCM keeps the 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 FCM is again closed to ground.

HEADLAMPS ON WITH WIPERS MODE
The circuitry of the Electromechanical Instrument Cluster (EMIC) provides an automatic headlamps on with wipers feature 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, 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 three minutes elapse without any automatic wipe cycles.

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 disabled the feature using the customer programmable features function. When the control knob on the control stalk of the right (wiper) multi-function switch is moved to one of the five DELAY interval positions the SCM sends an electronic wiper switch delay message to the FCM, then the FCM electronic intermittent wipe logic circuit responds by calculating the correct length of time between wiper sweeps based upon the selected delay interval input.

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

The FCM logic is also programmed to provide vehicle speed sensitivity to the selected intermittent wipe delay intervals. In order to provide this feature the FCM 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 stalk of the right (wiper) multi-function switch is moved downward to the momentary MIST position, the SCM sends an electronic message to the FCM, then the FCM energizes the wiper on/off relay for as long as the mist switch is held closed, then de-energizes the relay when the state of the mist switch changes to open, parking the wiper blades near the base of the windshield. The FCM 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 Mist switch is held closed.

WASH MODE
When the control stalk of the right (wiper) multi-function switch is pulled rearward to the front momentary WASH position for more than about one-half second with the wiper system operating, the SCM sends an electronic washer switch message to the FCM, which 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 wash switch is held closed and to be de-energize when the control stalk is released.

When the control stalk is pulled rearward to the front momentary WASH position while the front wiper system is operating in one of the DELAY interval (or sensitivity level with automatic wiper) positions, the washer pump/motor operation is the same. However, the FCM also energizes the wiper on/off relay to override the selected delay interval or sensitivity level and operate the front wiper motor in a continuous low speed mode for as long as the control stalk is held in the front momentary WASH position, then de-energizes the relay and reverts to the selected delay interval or sensitivity level several wipe cycles after the control stalk is released. If the wash switch is held closed for more than approximately 10 seconds, the FCM will suspend washer pump/motor operation until the control stalk is released for about 2 seconds, then cycled back to the WASH position.

WIPE-AFTER-WASH MODE
When the control stalk of the right (wiper) multi-function switch is pulled rearward to the front momentary WASH position for more than about one-half second while the wiper system is not operating, the SCM sends an electronic washer switch message to the FCM, which directs battery current and ground to the washer pump/motor and energizes the wiper on/off relay. This will cause the washer pump to operate in the front wash direction and operate the wiper motor in a continuous low speed mode for as long as the wash switch is held closed (up to approximately 10 seconds). When the control stalk is released, the FCM de-energizes the washer pump/motor, but allows the wiper motor to operate for two additional wipe cycles before it de-energizes the wiper on/off relay and parks the wiper blades near the base of the windshield.

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

REAR




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 outside liftgate flip-up glass surface that might be encountered while driving the vehicle under numerous types of inclement operating conditions.

The vehicle operator initiates all rear wiper and washer system functions with the control sleeve (3) on the control stalk (1) of the right multi-function switch that extends from the right side of the steering column, just below the steering wheel. Rotating the control sleeve on the control stalk to the various detent and momentary positions selects the rear wiper and washer system operating modes. The multi-function switch provides resistor multiplexed inputs to the Steering Control Module (SCM) for all of the rear wiper and washer system functions.

The SCM sends an electronic rear wiper/washer switch status message over the Controller Area Network (CAN) data bus to the Front Control Module (FCM) indicating the selected rear wiper and washer system operating mode. 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. The SCM also provides hard wired control 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/washer system operation is completely controlled by the SCM 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 right multi-function switch circuitry receives a clean ground output from the SCM on a multi-function switch return circuit, then provides resistor multiplexed inputs to the SCM to indicate the selected rear wiper and washer system operating mode.

The hard wired circuits and components of the rear wiper and washer system may be diagnosed and tested using conventional diagnostic tools and procedures. However, conventional diagnostic methods may not prove conclusive in the diagnosis of the SCM, the FCM or the electronic message inputs to or outputs from the SCM or the FCM that control the rear wiper and washer system operating modes. The most reliable, efficient, and accurate means to diagnose the SCM or the FCM inputs and outputs related to the various rear wiper and washer system operating modes requires the use of a diagnostic scan tool.

OPERATING MODES
Following are paragraphs that briefly describe the operation of each of the rear wiper and washer system operating modes.

CONTINUOUS WIPE MODE
When the continuous wipe position of the control sleeve on the control stalk of the multi-function switch is selected the SCM sends an electronic rear wiper switch status message to the FCM, which energizes the rear wiper relay. This directs battery current through the normally open contacts of the energized rear wiper relay to enable the rear wiper module. The SCM also provides a hard wired output to the rear wiper module indicating the selected mode, and the rear wiper module energizes the rear wiper motor causing the wipers to cycle at a fixed speed.

INTERMITTENT WIPE MODE
When the intermittent wipe position of the control sleeve on the control stalk of the multi-function switch is selected the SCM sends an electronic rear wiper switch status message to the FCM, which energizes the rear wiper relay. This directs battery current through the normally open contacts of the energized rear wiper relay to enable the rear wiper module. The SCM also provides a hard wired output to the rear wiper module indicating the selected mode, and the rear wiper module energizes the rear wiper motor causing the wipers to cycle at a predetermined fixed delay interval between wiper sweeps.

WASH MODE
When the control sleeve of the right multi-function switch is rotated counterclockwise to the rear momentary Wash position for more than about one-half second with the rear wiper system operating, the SCM sends an electronic washer switch status message to the FCM, which directs battery current and ground to the washer pump/motor unit. This will cause the washer pump to be energized in the rear washer direction for as long as the switch is held closed (up to approximately ten seconds) and to be de-energized when the control sleeve is released. The SCM also provides a hard wired output to the rear wiper module indicating the selected mode and if the rear wipers are operating in the intermittent mode, the rear wiper module operates the rear wiper motor at a fixed speed until the control sleeve is released.

WIPE-AFTER-WASH MODE
When the control sleeve of the right multi-function switch is rotated clockwise to the rear momentary Wash position for more than about one-half second while the rear wiper system is not operating, the SCM sends an electronic washer switch status message to the FCM, which directs battery current and ground to the washer pump/motor unit and energizes the rear wiper relay. This will cause the washer pump to be energized in the rear washer direction and the rear wiper module to be enabled for as long as the switch is held closed (up to approximately ten seconds) and to be de-energized when the control sleeve is released. and operate the rear wiper motor in a continuous speed mode for as long as the rear Wash switch is held closed (up to approximately ten seconds). The SCM also provides a hard wired output to the rear wiper module indicating the selected mode and the rear wiper module operates the rear wiper motor at a fixed speed until the control sleeve is released plus two additional wipe cycles before the SCM de-energizes the rear wiper relay and parks the rear wiper blade.