Chevrolet Equinox Service Manual: Wiper/Washer System Description and Operation

Wiper/Washer System Components

The wiper/washer system consists of the following electrical components:

Windshield Wiper RelayWindshield Wiper Speed Control RelayWindshield Washer Pump RelayWindshield Washer PumpWindshield Wiper MotorWindshield Wiper/Washer SwitchWindshield Wiper Motor FuseWindshield Washer Pump FuseBody Control Module (BCM)Rear Wiper MotorRear Wiper Motor FuseRear Wiper RelayRear Washer Pump RelayRear Washer Pump FuseWindshield Wiper System

The body control module (BCM) determines the front wipe/wash system mode of operationby monitoring several signals from the Windshield Wiper/Washer Switch as indicatedin the wiper switch.

The Windshield Wiper/Washer Switch receives a reference ground signal from the BCM.Each input of the BCM provides a switched battery pull-up for each front wiper/washerswitch output signal it receives. All the BCM inputs are recognized as active whenthe wiper switch provides a path to the referenced ground signal. The first signalreceived by the BCM is the result of 6 resistors in the front wiper switch configuredas a resistor laddernetwork. This signal is connected to a BCM analog to digital input. Depending on thefunction selected (High, Low, Intermittent 1 thru 5, Mist, Off), the Windshield Wiper/WasherSwitch connects a different set of resistors into the circuit resulting in differentvoltages appearing on the BCM A/D input. By monitoring this voltage, the BCM determineshow to control the wiper motor On/Off Relay. It should be noted that High, Low, andMist allhave the same value on this signal circuit. The second signal received from the frontwiper switch is active only when the front wiper switch is in the high speed wiperposition. When the wiper switch is not in the high speed position, the switch is openand the signal circuit is pulled to battery by the BCM. When the wiper switch is inthe high speed position, the switch pulls the circuit low. The BCM determines howto control the Wiper high/lowspeed relay from this input. The third signal received from the front wiper switchis from the momentary windshield wash control switch. When the washer switch is notactive the switch is open and the signal circuit is pulled to battery by the BCM.When the washer switch is active, the switch pulls the circuit low. The BCM controlsthe windshield wash and windshield wash activated wiper operation based on this input.

The BCM controls Windshield Wiper Motor operation through two output signals and themonitoring of one input signal. The two outputs (one high side drive, one low sidedrive) are used to control two external wiper motor relays: Windshield Wiper Motoron/off relay: which provides the wiper motor with battery power when it is activatedby the high side drive signal (switched battery) from the BCM. When left deactivated,the normally closedcontacts provide a ground to the wiper motor. Wiper high/low speed relay: when activatedby a low side drive signal (ground) from the BCM, it switches the power supplied bythe wiper motors on/off relay to the motors high speed input. When left deactivated,the normally closed contacts connect the power supplied by the wiper motors on/offrelay to the motors low speed input. The input used by the BCM is from the park switchlocated in the wipermotor assembly. When the wiper blades are not in the park position, the wiper parkswitch is open and the circuit is pulled up to battery by the BCM. When the wiperblades are in the park position at the bottom of the glass, the wiper park switchcloses to ground pulling the park signal circuit low.

To initiate low speed operation, the BCM only energizes the front Windshield WiperMotor on/off relay. This allows battery voltage from the wiper fuse to be appliedthrough the switched contacts of the wiper motor on/off relay, through the normallyclosed contacts of the wiper high/low speed relay, to the low speed control circuitof the windshield wiper motor.

Redundant high speed switch pass through. The BCM provides redundant circuitry whichplaces battery power on its wiper motor on/off relay output with activation of itslow assertion high speed wiper switch input. The BCM shall be capable of doing this,even if the module has lost all microprocessor control. This redundant circuit shallsupply power while in the RUN and CRANK power modes. however; while in the CRANK powermode, the passthrough shall only be active if the BCM is NOT in a computer operating properly state.

To initiate high speed operation, the BCM energizes both the Windshield Wiper Motoron/off relay and the wiper high/low speed relay . This allows battery voltage fromthe wiper fuse to be applied through the switched contacts of the wiper motor on/offrelay, through the switched contacts of the wiper high/low speed relay, to the highspeed control circuit of the windshield wiper motor.

Parking the wiper motor. In order to perform an accurate read of the park switch andto ensure the wipers will come to rest while still in the park position, parking ofthe wipers only occurs while in a low speed wiper mode. This requires that if thewipers are performing a high speed wiper operation at the time they are required topark, the BCM shall transition the Wipers to low speed by deactivating the wiper high/lowrelay beforeattempting to park. In order to park the wipers, the BCM monitors the park circuituntil the park switch pulls the park circuit to ground. At this time, the BCM willimmediately deactivate the wiper motor on/off relay. The relay contacts will switchback to their normally closed position and will apply ground to the wiper motor powerinputs through the normally closed contacts of the wiper high/low relay. This deactivatesand dynamically brakesthe wiper motor in the park position. When the wiper switch is turned to the OFF positionwhile the wiper motor is somewhere in mid-cycle, the BCM will continue to operatethe motor until the wipers reach the park position. If the BCM is running the wipermotor and does not see a state transition of the park switch after 8 s, the wiperswill stop immediately when the wiper switch is turned to OFF. If the ignition is turnedOFF while the wipersare in mid-cycle, the wipers will stop immediately, regardless of position. The BCMwill park the wipers next time the ignition is turned ON.

The windshield wiper system MIST operation is identical to LOW speed operation, exceptthat the MIST switch is a press and release type switch. When the wiper switch ismoved to the MIST position and released, low speed wiper motor operation is startedand will continue until 1 cycle is complete. If the wiper switch is moved to the MISTposition and held, the wiper motor will operate in the LOW speed mode until the switchis released.

Windshield wiper intermittent operation is a low speed wiper motor function with avariable delay interval between the wiper motor cycles. The duration of the delayis controlled by the front wiper control switches intermittent 1 through intermittent5 settings. The wiper operation is as follows

The BCM will initiate a single wipe by activating its windshield wiper ON/OFF relayoutput.At the completion of a single wipe, the BCM will park the wipers as described above.The BCM will then pause the wipers in their park position for the time duration associatedwith intermittent delay switch setting.When the delay time expires repeat Steps 1 and 3 until the system is turned off ortaken out of intermittent mode. If the wiper switch is moved from a longer delay intervalto a shorter delay interval, the BCM will command an immediate wipe cycle and resetthe delay timer to the shorter delay interval.

Intermittent wiper operation may be vehicle speed sensitive. When enabled, the speedcompensated intermittent feature causes the intermittent wiper delay intervals tobecome shorter as a function of increased speed. As vehicle speed is reduced the intervalswill become closer to the predetermined

Windshield Washer System

The BCM controls the windshield wash operation and windshield wash activated wiperoperation. When the BCM detects the activation of the momentary windshield wash controlswitch, it activates its washer pump relay drive output which supplies battery powerto the coil of the washer pump relay. This energizes the relay, which switches batterypower to the pump motor. The BCM will also activate continuous low speed windshieldwipes as describedabove. Upon deactivation of the windshield wash control switch, the body control module(BCM) shall deactivate the wash motor and will also park the wiper motor as describedabove unless the drip wipe feature is enabled. On some vehicles the drip wipe featurewill be enabled and cause the system to provide additional wiping of the windshieldafter the switch has been released and fluid is no longer being applied. The windshieldwasher switchfeature may attempt to detect a stuck switch. When enabled, activation of the washfeature shall be limited to 10 seconds.

On vehicles with the Rear Wash feature a single reversing wash motor may be utilizedfor both the front and rear wash operation. In this system the wash motor is operatedin one direction to spray fluid on the front windshield and then operated in the reversedirection to spray fluid on the rear window. The BCM Controls the reversing wash motorthrough two High Side Drive outputs. One controls the Windshield Wiper Motor Relayand onecontrols the Rear Wiper Relay.

Rear Wiper System

On vehicles equipped with a Rear Wiper, the BCM determines of the Rear Wipe/Wash SystemMode of Operation by monitoring the multiplexed output of the Windshield Wiper/WasherSwitch. The Rear Wiper Relay uses a reference ground signal from the BCM. The BCMprovides a switched Battery pull-up for the Rear Wiper Relay switch output signalit receives. All the BCM inputs are recognized as active when the Rear Wiper Relayswitch provides apath to the referenced ground signal. The Rear Wiper/Washer signal received by theBCM is the result of 3 resistors in the Windshield Wiper/Washer Switch configuredas a resistor ladder network. This signal is connected to a BCM Analog to DigitalInput which also provides a switched Battery pull-up for the circuit. Depending onthe function selected (Low, Intermittent, Off, Wash), the Rear Wiper Control Switchconnects a different set of resistorsinto the circuit resulting in different voltages appearing on the BCM A/D input. Bymonitoring this voltage, the BCM determines how to control the Rear Wiper Relay andthe Rear Washer Relay.

The BCM Controls the single speed Rear Wiper Motor by its Active High output to theexternal Rear Wiper Relay. When the BCM activates its output and applies Battery tothe coil of the relay, the relay energizes, allowing Battery voltage from the fuseto be applied through the switched contacts of the Rear Wiper Relay to the Rear WiperMotors control input. The motor then operates continuously at low speed. The BCM doesnot control theparking of the Rear Wiper Motor, it is self parking. When the BCM deactivates itsoutput, the contacts of the Rear Wiper Relay switch back to ground which will be usedby the wiper for Dynamic Braking. The Rear Wipers internal park switch and circuitrywill sustain motor operation until the wiper arm has returned to its Park position.

Rear Wash

When the Body Control Module detects that the Rear wiper/washer switch has activatedthe momentary Wash switch, it activates a High Side Drive output which supplies Batteryto the coil of the Rear Washer Pump Relay. This energizes the Relay, which switchesBattery Power to the Washer Pump Motor. The BCM will also activate continuous LowSpeed Windshield Wipers as described above. The BCM software will attempt to detecta stuck Rear WashSwitch. A stuck Rear Wash Switch condition is detected if the Rear Wash Motor RelayOutput has been continuously active for 10 seconds or more. Upon detecting this theBCM will fail soft the state of the Rear Wash Control to Inactive. This shall causethe System to perform as if the momentary Wash control had been released.