Wiper and Washer Systems: Description and Operation

WIPER/WASHER SYSTEM DESCRIPTION AND OPERATION

WIPER/WASHER SYSTEM COMPONENTS
The Wiper/Washer System consists of the following components:
- Windshield wiper/washer switch
- Body control module (BCM)
- Wiper micro relay
- Wiper 2 relay
- Wiper diode
- Windshield wiper motor
- Windshield washer pump
- Windshield washer nozzles
- Windshield washer solvent container
- Windshield wiper arm and blade assemblies
- Windshield wiper transmission
- WIP/WASH 10A fuse
- WIPER 25A fuse

Refer to Wiper/Washer System Component Views.

WIPER/WASHER SYSTEM DESCRIPTION
The body control module (BCM) controls wiper motor low speed operation. The washer pump and high speed operation are controlled directly by the wiper/washer switch. The windshield wiper/washer switch supplies voltage on the signal circuits to the BCM for windshield wiper/washer operation. When WASH, MIST, DELAY, LOW, or HIGH is detected, the BCM energizes the wiper micro relay by suppling voltage to the relay coil. This allows battery voltage from the WIPER fuse to flow through the relay switched input then through the contacts and out the relay switched output to the wiper 2 relay switch contacts. Since the wiper 2 relay switch contacts are normally closed to the low speed circuit of the windshield wiper motor, the motor will operate at low speed.

Wash Operation
In the WASH position windshield wiper/washer switch supplies voltage to the windshield washer pump. The body control module (BCM) monitors voltage on this circuit to detect when a wash cycle is requested so it can enable the wipers. After a short delay, the BCM energizes the wiper relay which will operate the windshield wiper motor at low speed. The wiper motor will continue to operate for 2 wipe cycles after the wash switch is released.

Mist Operation
Windshield Wiper/Washer System mist operation is identical to low operation, except that the mist switch is a press and release type switch. When the wiper switch is moved to the mist position and released, low speed wiper motor operation is started and will continue until 1 cycle is complete. If the wiper switch is moved to the MIST position and held, the wiper motor will operate in the LOW mode until the switch is released.

In the MIST position, voltage is supplied through an internal resistor to the signal circuit of the windshield wiper/washer switch for the body control module (BCM). The BCM will energize the wiper micro relay which will operate the windshield wiper motor at low speed.

Intermittent Operation
Windshield wiper delay operation is a low speed wiper motor function with a variable delay interval between the wiper motor cycles. The delay interval is determined by a series of 5 resistors within the wiper/washer switch. During delay wiper operation the signal circuit voltage is further reduced through the delay resistors. The body control module (BCM) monitors the voltage on the signal circuit to determine the delay interval between the low speed wiper motor cycles.

If the wiper switch is moved from a longer delay interval to a shorter delay interval, the BCM will command an immediate wipe cycle, and reset the delay timer to the shorter delay interval.

Low Speed Operation
When the wiper switch is in the Low position, voltage is supplied through an internal resistor to the signal circuit. The body control module (BCM) monitors the windshield wiper switch signal 1 circuit, and energizes the wiper micro relay which will operate the windshield wiper motor. The wiper motor will operate at low speed, since the wiper 2 relay is de-energized. Low speed can also be commanded with a scan tool, by commanding Wiper Relay Cmd. ON and OFF. Refer to Scan Tool Output Controls.

High Speed Operation
In the High position, the windshield wiper/washer switch supplies voltage to both the wiper micro relay and wiper 2 relay coils. This energizes both relays and allows battery voltage from the wiper micro relay switched output to the switched input of the wiper 2 relay through its contacts and out the switched output of the wiper 2 relay to the high speed circuit of the windshield wiper motor. The windshield wiper motor will operate at high speed. During high speed wiper motor operation the wiper switch signal circuit is at the low speed signal voltage, and the body control module (BCM) supplies redundant voltage to the wiper relay via the wiper diode.

Park Position Operation
Windshield wiper motor park operation is controlled by the body control module (BCM) using an input from the park switch within the wiper motor assembly. The BCM monitors the windshield wiper motor park switch circuit to determine if the windshield wiper blades are at the bottom of the glass. The circuit will be pulled to ground by the wiper motor park switch while the windshield wiper motor is operating. When the wiper switch is turned to the OFF position while the wiper motor is somewhere in mid-cycle, the BCM will continue to operate the motor until the wipers reach the park position. If the ignition is turned OFF while the wipers are in mid-cycle, the wipers will stop immediately where they are. The BCM will park the wipers the next time the ignition is turned ON.

The wipers will not park when they are commanded ON and OFF with a scan tool. The BCM will park the wipers the next time the wiper switch is turned ON and OFF.

The BCM provides stall protection for the wiper motor by monitoring the park switch. If the park switch does not transition for 3 seconds while the wipers are operating, the BCM will assume that the wiper motor is stalled, and will de-energize the wiper relay until the wiper switch is cycled OFF and ON again.

WINDSHIELD WIPER/WASHER SYSTEM POWER AND GROUND
With the ignition in the ON position, accessory voltage is supplied through the WIPE/WASH 10A fuse in the underhood fuse block to the wiper/washer switch. Refer to Wiper/Washer System Schematics.

G101 provides ground for the following:
- Windshield washer pump
- Windshield wiper motor
- Wiper micro relay
- Wiper 2 relay

DIAGNOSTIC TROUBLE CODES (DTCS)
The body control module (BCM) monitors the voltage on the windshield wiper switch signal 2 circuit for diagnostic purposes. If the circuit is shorted to voltage while the driver is commanded OFF, the BCM will store DTC B3717. If the circuit is shorted to ground while the driver is commanded ON, the BCM will store DTC B3718.