Wiper and Washer Systems: Description and Operation
Front Wiper/WasherHow the Circuit Works
The MICU (in the under-hood fuse/relay box), the combination switch control unit, the control block (in the under-hood fuse/relay box) and the multiple integrated control system control the wiper/washer circuit. The front and rear washer motor relays, intermittent wiper relay, and windshield wiper high relay are incorporated in the under-hood fuse/relay box.
An HDS Tester can test the control unit components and read Diagnostic Trouble Codes (DTCs) within the multiplex integrated control system. There are more than 80 multiplex system DTCs.
The windshield wiper motor and washer motor can also be tested manually without an HDS Tester.
Power Supply
Fuse 7 (in the under-dash fuse/relay box) supplies battery voltage at all times to the MICU and the combination switch control unit.
Fuse 21 (in the under-dash fuse/relay box) supplies battery voltage with the ignition switch in ON (II), to the MICU, the control block and the combination switch control unit.
Fuse 31 (in the under-dash fuse/relay box) supplies battery voltage with the ignition switch in ON (II) or START (III) to the intermittent wiper relay coil, the windshield wiper high relay coil, and the contacts of the front washer motor relay and the rear washer motor relay.
Fuse 11 (in the under-dash fuse/relay box) supplies battery voltage with the ignition switch in ON (II) or START (III), to the intermittent wiper relay contact and to the windshield wiper motor.
Mist
Moving the windshield wiper switch to MIST, inputs the mist signal to the combination switch control unit. The combination switch control unit communicates the mist information via the B-CAN network to the control block in the under-hood fuse/relay box. The control block grounds the intermittent wiper relay coil, energizing the relay. The energized intermittent wiper relay supplies battery voltage through the static windshield wiper high relay to the high winding of the windshield wiper motor, causing the motor to run in high.
The control block grounds the intermittent wiper relay just long enough to start the motor running. As soon as the motor starts running, the mechanical park/run switch built into the motor moves from PARK to RUN. The park/run switch supplies battery voltage through the static intermittent wiper relay and the static windshield wiper high relay to the high winding of the windshield wiper motor.
Holding the wiper switch in MIST for multiple wiper cycles, alternates the PARK/RUN switch between PARK and RUN.
Releasing the wiper switch from MIST stops the wipers when they return to PARK due to the lack of battery voltage through the park/run switch or static intermittent wiper relay.
Intermittent
Moving the windshield wiper switch to INTERMITTENT, inputs the intermittent signal and the signal for the intermittent dwell time controller to the combination switch control unit. The combination switch control unit communicates the intermittent dwell time information via the B-CAN network to the control block in the under-hood fuse/relay box. The control block grounds the intermittent wiper and windshield wiper high relay coils energizing both relays. The energized relays supply battery voltage to the low winding of the windshield wiper motor causing the motor to run in low.
The control block grounds the intermittent wiper relay long just enough to start the motor running, but continues grounding the windshield wiper high relay. As soon as the motor starts running, the mechanical park/run switch built into the motor moves from PARK to RUN. The park/run switch supplies battery voltage through the static intermittent wiper relay and the energized windshield wiper high relay to the low winding of the windshield wiper motor.
If the wiper switch is in INTERMITTENT for multiple wiper cycles, the PARK/RUN switch alternates between PARK and RUN.
Moving the windshield wiper switch to OFF sends the off signal to the combination switch control unit. The combination switch control unit communicates that information via the B-CAN network to the control block in the under-hood fuse/relay box. The wipers will stop when they return to PARK due of a lack of battery voltage through the park/run switch or static intermittent wiper relay.
Low Speed
Moving the windshield wiper switch to LOW sends the low signal to the combination switch control unit. The combination switch control unit communicates the low speed information via the B-CAN network to the control block in the under-hood fuse/relay box. The control block grounds the intermittent wiper and windshield wiper high relay coils energizing both relays. The energized relays supply battery voltage to the low winding of the windshield wiper motor causing the motor to run in low.
The control block grounds the intermittent wiper relay long enough to start the motor running, but continues grounding the windshield wiper high relay. As soon as the motor starts running, the mechanical park/run switch built into the motor moves from PARK to RUN. The park/run switch supplies battery voltage through the static intermittent wiper relay and the energized windshield wiper high relay to the low winding of the windshield wiper motor.
If the wiper switch is in LOW for multiple wiper cycles, the PARK/RUN switch alternates between PARK and RUN.
Moving the windshield wiper switch to OFF sends the off signal to the combination switch control unit. The combination switch control unit communicates that information via the B-CAN network to the control block in the under-hood fuse/relay box. The wipers will stop when they return to PARK due of a lack of battery voltage through the park/run switch or static intermittent wiper relay.
High Speed
Moving the windshield wiper switch to HIGH sends the high signal to the combination switch control unit. The combination switch control unit communicates that information via the B-CAN network to the control block in the under-hood fuse/relay box. The control block grounds the intermittent wiper relay coil energizing it. The energized intermittent wiper relay supplies battery voltage through the static windshield wiper high relay to the high winding of the windshield wiper motor, causing the motor to run in high.
The control block grounds the intermittent wiper relay long enough to start the motor running. As soon as the motor starts running, the mechanical park/run switch built into the motor moves from PARK to RUN. The park/run switch supplies battery voltage through the static intermittent wiper relay and the static windshield wiper high relay to the high winding of the windshield wiper motor.
If the wiper switch is in HIGH for multiple wiper cycles, the PARK/RUN switch alternates between PARK and RUN.
Moving the windshield wiper switch to OFF sends the off signal to the combination switch control unit. The combination switch control unit communicates that information via the B-CAN network to the control block in the under-hood fuse/relay box. The wipers will stop when they return to PARK due of a lack of battery voltage through the park/run switch or static intermittent wiper relay.
The wiper back-up circuit provides the wiper signal from the combination wiper switch directly to the control block in the under-hood fuse/relay box in the event of B-CAN network failure.
Washer
Moving the windshield wiper switch to WASH sends the wash signal to the combination switch control unit. The combination switch control unit communicates that information via the B-CAN communication network to the control block in the under-hood fuse/relay box. The control block energizes the front washer motor relay, supplying battery voltage to the washer motor.
The control block also grounds the intermittent wiper relay coil providing battery voltage through the static windshield wiper high relay to the high winding of the windshield wiper motor. The washer motor pumps washer fluid onto the windshield, and the windshield wiper motor runs in high. As soon as the motor starts running, the mechanical park/run switch built into the motor moves from PARK to RUN.