Wiper and Washer Systems: Description and Operation

Front Wiper/Washer

How the Circuit Works

The wiper/washer system is a multiplex controlled system. The MICU and wiper/washer switch are the main operation controls of the front wiper/washer system.

Testing the MICU and reading Diagnostic Trouble Codes (DTCs) within the multiplex integrated control system can be done using the HDS Tester. There are more than 80 multiplex system DTCs. The windshield wiper motor and washer motor can be tested manually without an HDS Tester.

Power Supply

With the ignition switch in ON (II), fuse 38 (in the under-dash fuse/relay box) supplies battery voltage to the MICU.

Mist

When the windshield wiper switch is moved to MIST, the signal for mist is sent to the MICU. The MICU supplies battery voltage to the high winding of the windshield wiper motor causing the motor to run in high. As soon as the motor starts running, the mechanical park/run switch built into the motor moves from PARK to RUN removing ground from the FR WIP AS input to the MICU. If the switch is held in MIST for multiple wiper cycles, the PARK/RUN signal will alternate between PARK and RUN, indicating wiper position to the MICU.

Intermittent (LX)

When the windshield wiper switch is moved to INTERMITTENT, the signal for intermittent is sent to the MICU. Dwell time is fixed. The MICU supplies battery voltage to the low winding of the windshield wiper motor causing the motor to run in low. As soon as the motor starts running, the mechanical park/run switch built into the motor moves from PARK to RUN removing ground from the FR WIP AS input to the MICU. If the switch is in INTERMITTENT for multiple wiper cycles, the PARK/RUN signal will alternate between PARK and RUN indicating wiper position to the MICU.

Intermittent (EX, EX-L)

When the windshield wiper switch is moved to INTERMITTENT, the signal for intermittent and the signal for the intermittent dwell time controller are sent to the MICU. Dwell time is varied by adjusting the intermittent dwell time controller. The MICU supplies battery voltage to the low winding of the windshield wiper motor causing the motor to run in low. As soon as the motor starts running, the mechanical park/run switch built into the motor moves from PARK to RUN removing ground from the FR WIP AS input to the MICU. If the switch is in INTERMITTENT for multiple wiper cycles, the PARK/RUN signal will alternate between PARK and RUN indicating wiper position to the MICU.

Low Speed

When the windshield wiper switch is moved to LOW, the signal for low is sent to the MICU. The MICU supplies battery voltage to the low winding of the windshield wiper motor causing the motor to run in low. As soon as the motor starts running, the mechanical park/run switch built into the motor will move from PARK to RUN, removing ground from the FR WIP AS input to the MICU. If the switch is in LOW for multiple wiper cycles, the PARK/RUN signal will alternate between PARK and RUN indicating wiper position to the MICU.

When the windshield wiper switch is moved to OFF, the signal for off is sent to the MICU. As soon as the wipers reach the PARK position, the MICU removes battery voltage from the low winding of the windshield wiper motor.

High Speed

Moving the windshield wiper switch to HIGH sends a high speed input to the MICU. The MICU supplies battery voltage to the high winding of the windshield wiper motor, running the motor in high. As soon as the motor starts running, the mechanical park/run switch built into the motor moves from PARK to RUN. With the motor running, the mechanical park/run switch is in RUN, removing ground from the FR WIP AS input to the MICU. If the switch is in HIGH for multiple wiper cycles, the PARK/RUN signal alternates between PARK and RUN indicating wiper position to the MICU.

When the windshield wiper switch is moved to OFF, the signal for off is sent to the MICU. As soon as the wipers reach the PARK position, the MICU removes battery voltage from the high winding of the windshield wiper motor.

Washer

Moving the windshield wiper switch to WASH, sends a wash signal to the MICU. The MICU supplies battery voltage to the windshield washer motor and to the high winding of the windshield wiper motor. The windshield washer motor pumps washer fluid onto the windshield and the windshield wiper motor runs in high. As soon as the wiper motor starts running, the mechanical park/run switch built in the motor moves from PARK to RUN.