Headlamp Windshield Washer Pump - Operation

HEADLAMP

Headlamp washer pump/motor unit operation is completely controlled by the Body Control Module (BCM) (also known as the Common Body Controller/CBC) logic circuits based upon electronic wash request and lighting request message inputs received from the Steering Angle Sensor (SAS) integral to the clockspring over the Controller Area Network (CAN) data bus. The SAS monitors electronic washer switch and lighting switch status messages received over the Local Interface Network (LIN) data bus from the Steering Control Module (SCM). The SCM monitors analog and resistor multiplexed inputs from the front washer switch circuitry contained within the multi-function switch to determine the proper washer switch status messages to send.

The headlamp washer relay control coil operates on battery voltage received from the run relay, so it is only functional while the engine is running. In addition, the BCM will only allow the headlamp washers to operate when the headlamps are turned ON. The BCM uses a low side driver 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 pump/motor unit 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 pump/motor or the electronic controls or 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 pump/motor unit or the electronic controls and communication related to headlamp washer pump/motor unit operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.