Section 67 (Wiper System & Washer System (Service Information)): Operation: Headlamp
The headlamp washer system is designed to provide the vehicle operator with a convenient, safe, and reliable means of maintaining High Intensity Discharge (HID) 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 stalk of the right multifunction switch that extends from the right side of the steering column, just below the steering wheel. While the HID headlamp low beams are turned On, pulling the control stalk rearward towards the steering wheel beyond the actuation point for more than about 100 milliseconds (0.10 second) activates the front washer pump/motor. During any ignition cycle, the first time the front washer pump/motor is activated and; thereafter, each eleventh time the front washer pump/motor is activated, the headlamp washer pump/motor cycle is also activated.
Each time the headlamp washers are employed, the headlamp washer pump/motor is activated using a two shot strategy. The initial shot wets the lenses of the HID headlamps. The lenses are then allowed to soak for a short interval before a second shot is dispensed to rinse the lenses. Each shot results in several high pressure streams of washer fluid being dispensed upon the headlamp lenses by the headlamp washer nozzles.
Headlamp washer system operation is completely controlled by the Body Control Module (BCM) logic circuits based upon programming and electronic wash command message inputs received from the microcontroller internal to the Steering Column Control Module (SCCM) for all of the wiper and washer system functions. The SCCM microcontroller then sends electronic wiper switch and washer switch status messages to the BCM over the Controller Area Network (CAN) data bus requesting the appropriate wiper and washer system operating modes.
The BCM will only allow this system to operate when the status of the ignition is On and the headlamp low beams are turned On. When the appropriate inputs are monitored and the appropriate programming requirements have been met, the BCM provides the appropriate output to the headlamp washer relay integral to the Printed Circuit Board (PCB) within the Power Distribution Center (PDC). The BCM uses a Low Side Driver (LSD) to energize or de-energize the headlamp washer relay which, in turn, controls the operation of the headlamp washer pump/motor unit.
The hard wired 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.