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 (rain sensing) wiper system and it is enabled, when the control knob on the control stalk of the multifunction switch is moved to one of the four sensitivity positions, the SCCM microcontroller sends an electronic wiper switch sensitivity  message to the BCM over the CAN data bus. The BCM, which is also a Local Interface Network (LIN) data bus master node, relays the wiper switch sensitivity  message to the Light Rain Sensor Module (LRSM), which is a LIN slave node, 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 BCM over the LIN data bus. Then the BCM 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 sensitivity position of the control knob is designed to provide optimal wiper performance for most typical driving requirements. The BCM logic is also programmed to provide an immediate wipe cycle each time the control knob on the control stalk of the multifunction 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 of the Settings menu, 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 (N  ) position while the status of the ignition switch is ON, 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 km/h (5 mph) 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 multifunction switch is selected the SCCM microcontroller sends an electronic wiper switch low  status message to the BCM over the CAN data bus. The BCM then provides the appropriate outputs to the wiper on-off and wiper high-low relays within the PDC to direct 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 SCCM microcontroller sends an electronic wiper switch high  status message to the BCM. The BCM then provides the appropriate outputs to the wiper on-off and wiper high-low relays within the PDC to direct 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 multifunction switch control knob is selected, the SCCM microcontroller sends an electronic wiper switch off  status 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 hardwired park switch sense input to the BCM. The BCM provides the appropriate outputs to the wiper on-off and wiper high-low relays within the PDC to de-energize 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 provides the appropriate outputs to the wiper on-off and wiper high-low relays within the PDC to continue 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.

• Headlamps ON With Wipers Mode  - The circuitry and programming of the BCM 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 Settings menu. If this feature is enabled, when the headlamp switch is in the Automatic (A  ) 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 (rain sensing) 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 (rain sensing) wiper system that have been disabled using the Customer Programmable Features function of the Settings menu.

  When the control knob on the control stalk of the multifunction switch is moved to one of the four Delay (Intermittent) interval positions the SCCM microcontroller sends an electronic wiper switch delay interval  status message to the BCM. Then the BCM 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 hardwired park switch sense input. This input allows the BCM to determine the proper intervals at which to provide the appropriate outputs to the wiper on-off and high-low relays on the PCB within the PDC 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 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 Antilock Brake System (ABS) module and doubles the selected delay interval whenever the vehicle speed is about 16 km/h (10 mph) or less.

• Mist Wipe Mode  - When the control knob of the multifunction switch is rotated downward to the momentary Mist position, the SCCM microcontroller sends an electronic wiper mist mode  status message to the BCM. The BCM then provides the appropriate outputs to the wiper on-off and wiper high-low relays on the PCB within the PDC to energize the low speed brush of the wiper motor for as long as the switch is held closed, then de-energize the motor when the state of the Mist 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 Mist switch is held closed.
• Wash Mode  - When the control knob of the multifunction 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 SCCM microcontroller sends an electronic washer switch  status 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 (or sensitivity level with automatic or rain sensing wipers) positions, the washer pump/motor operation is the same. However, the BCM 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 BCM will suspend washer pump/motor operation until the control knob is released for about 2 seconds, then is cycled back to the Wash position.

• Wipe-After-Wash Mode  - When the control knob of the multifunction 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 SCCM microcontroller sends an electronic washer switch  status message to the BCM. Then the BCM directs battery current and ground to operate the washer pump/motor in the front wash direction and provides the appropriate outputs to the wiper on-off and wiper high-low relays on the PCB within the PDC to energize 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 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 knob is released for about 2 seconds and then is 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 hardwired 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.