Headlamp Washer System: Operation
The headlamp washer system is designed to provide the vehicle operator with a convenient, safe, and reliable means of maintaining headlamp lighting performance. The various components of this system are designed to convert electrical energy produced by the vehicle electrical system into the hydraulic action of the washer system to apply washer fluid stored in an on-board reservoir to the lenses of the two front lamp units, removing excess accumulations of snow, ice, bugs, mud or other minor debris from the front lamps that might be encountered while driving the vehicle under numerous types of inclement operating conditions.
The vehicle operator initiates the headlamp washer system function using the control knob on the end of the multifunction switch control stalk that extends from the right side of the steering column, just below the steering wheel. While the headlamps are turned ON, activating the front washer pump/motor also activates the headlamp washer pump/motor in combination with the front washer pump/motor and then on an interval scheduled number of front washer activations after the first one, which is determined by the BCM programming. When the headlamp washer pump/motor unit is energized, hydraulic pressure builds within the headlamp washer system plumbing against the pressure of the return spring in each headlamp washer nozzle. Sufficient pressure causes the headlamp washer nozzles to telescope outward and to dispense high pressure washer fluid onto the lenses of both front lamp units for a pre-determined amount of time in milliseconds. When the headlamp washer is activated, the BCM commands the activation on for the pre-determined amount of time, turn off for a pre-determined amount of soak time, turn on again for a pre-determined amount of time and then finally off completely.
The headlamp washer activation counter resets to the first transition whenever the headlamp switch is cycled from ON to OFF, or if the ignition is cycled from RUN or ACC to OFF or START, then back to RUN or ACC.
Headlamp washer system operation is completely controlled by the Body Control Module (BCM) logic circuits based upon electronic wash command and lighting switch status message inputs received from the Instrument Panel Cluster (IPC) over the Controller Area Network (CAN) data bus. The IPC monitors electronic wash switch status message inputs received over the Local Interface Network (LIN) data bus from the Steering Column Control Module (SCCM) based upon multifunction switch positions and multiplex inputs received from the headlamp switch. The BCM will only allow this system to operate when the ignition switch is in the ON position and the headlamp low beams are turned ON. The BCM uses a high side driver to energize or de-energize the headlamp washer system relay which, in turn, controls the operation of the headlamp washer pump/motor unit.
The hardwired circuits and components of the headlamp 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 headlamp washer system or the electronic controls and communication between other modules and devices that provide some features of the headlamp washer system. The most reliable, efficient and accurate means to diagnose the headlamp washer system or the electronic controls and communication related to headlamp washer system operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.