Rear Wiper Operation (with EGM)

WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2004 Oldsmobile Bravada, 2004 GMC Envoy XUV, 2004 GMC Envoy XL, 2004 GMC Envoy, and 2004 Chevrolet TrailBlazer. However, it is still accessible from the selected car via links, so may be relevant.

The rear window wiper/washer switch is an input to the BCM. The requested rear wiper mode is sent to the EGM by the BCM, as a message on the serial data circuit. The rear window wiper motor is controlled by the EGM. The switch power circuit to the rear wiper/washer switch is a 12-volt reference supplied by the BCM. The rear wiper/washer switch is composed from a series of resistors and the switch position is determined by the voltage of the rear wiper/washer switch signal circuit to the BCM. The rear wiper/washer switch has continuity at all times and the BCM expects a rear wiper/washer switch signal voltage in all switch positions including OFF. The rear wiper motor is supplied battery positive voltage and ground. The EGM controls rear wiper motor operation through the rear window motor speed signal circuit. The rear window motor speed signal circuit is supplied a battery positive reference voltage by the rear window wiper motor module and is pulse width modulated to ground by the EGM. The duty cycle of the pulse width modulation determines the rear wiper motor operating mode. The rear window motor park signal circuit provides position status of the rear wiper to the EGM.

The rear wiper and washer operation is allowed if the following conditions are true:

Power mode is run or accessory.
Lower left ajar switch is closed.
Upper left ajar switch is closed.
Upper right ajar switch is closed.
Upper left dome switch is closed.
The end gate window is fully closed.
No end gate window express down, up, or down is requested.
No gate swing open or drop open is requested.

If rear wiper/washer operation is attempted and the end gate window is open the driver information center (DIC) displays "Tailgate Glass Down". If the rear wiper is not in the park position and an attempt to open end gate window is done, the DIC displays "Rear Wiper Obstruction".