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Windshield Wiper Operation

WARNING: This page is about a different car, the 2022 Cadillac CT5. However, it is still accessible from the selected car via links, so may be relevant.

The windshield wipers system allows the driver to clear the vehicle's windshield using a discrete switch or through an automatic rain sensing system. The windshield wiper system functions through a primary control, but also allows redundant high speed-only operation in the event of a system fault. The wiper systems uses the S82 Windshield Wiper/Washer Switch as the primary means of driver control, along with the B117A Windshield Outside Moisture/Ambient Light and Humidity Sensor to modulate intermittent wiper operation. The S82 Windshield Wiper/Washer Switch is a discrete input to the K9 Body Control Module. The K9 Body Control Module communicates with the B117A Windshield Outside Moisture/Ambient Light and Humidity Sensor and the M75 Windshield Wiper Motor via LIN to control wiper activation. The K9 Body Control Module communicates with the K219 Exterior Lighting Control Module over CAN, which controls B+ to the M75 Windshield Wiper Motor during operation.

Low Speed Wiper Operation 

The K9 Body Control Module interprets the ignition being switched to ON and the K9 Body Control Module responds by sending a CAN message to the K219 Exterior Lighting Control Module to supply B+ to the M75 Windshield Wiper Motor. The K219 Exterior Lighting Control Module controls the KR12B Windshield Wiper Relay by providing voltage to the coil side of the relay. This energizes the relay, closing the relay's high current switch, which supplies B+ to the M75 Windshield Wiper Motor. With the S82 Windshield Wiper/Washer Switch in the low speed position, the discrete signal circuit to the K9 Body Control Module is pulled down through two resistors in a resistor ladder to a low reference provided by the K9 Body Control Module. The K9 Body Control Module communicates with the M75 Windshield Wiper Motor via LIN, requesting consistent low speed wiping operation.

Intermittent Wiper Operation 

The K9 Body Control Module interprets the ignition being switched to ON and the K9 Body Control Module responds by sending a CAN message to the K219 Exterior Lighting Control Module to supply B+ to the M75 Windshield Wiper Motor. The K219 Exterior Lighting Control Module controls the KR12B Windshield Wiper Relay by providing voltage to the coil side of the relay. This energizes the relay, closing the relay's high current switch, which supplies B+ to the M75 Windshield Wiper Motor. With the S82 Windshield Wiper/Washer Switch in the intermittent position, the discrete signal circuit to the K9 Body Control Module is pulled down through a number of resistors within a resistor ladder to a low reference provided by the K9 Body Control Module. The number of resistors the signal travels through is dependent on the intermittent selection made on the S82 Windshield Wiper/Washer Switch. The K9 Body Control Module interprets this range of voltage pull-down as a request for intermittent wiper activation, with each pull-down voltage value equating an intermittent sensitivity level. The K9 Body Control Module communicates with the B117A Windshield Outside Moisture/Ambient Light and Humidity Sensor and M75 Windshield Wiper Motor via LIN. The B117A Windshield Outside Moisture/Ambient Light and Humidity Sensor utilizes windshield optics to determine the amount of water on the windshield and will communicate this info to the K9 Body Control Module and M75 Windshield Wiper Motor, which will vary wiping cadence based on the intermittent sensitivity selection on the S82 Windshield Wiper/Washer Switch and the amount of water on the windshield.

High Speed Wiper Operation 

The K9 Body Control Module interprets the ignition being switched to ON and the K9 Body Control Module responds by sending a CAN message to the K219 Exterior Lighting Control Module to supply B+ to the M75 Windshield Wiper Motor. The K219 Exterior Lighting Control Module controls the KR12B Windshield Wiper Relay by providing voltage to the coil side of the relay. This energizes the relay, closing the relay's high current switch, which supplies B+ to the M75 Windshield Wiper Motor. With the S82 Windshield Wiper/Washer Switch in the high speed position, the discrete signal circuit to the K9 Body Control Module is pulled down through two resistors in a resistor ladder to a low reference provided by the K9 Body Control Module. The K9 Body Control Module interprets this specific voltage pull-down as a request for wiper activation. In addition to this pull-down signal, a second switch in the S82 Windshield Wiper/Washer Switch is also pulled down to low reference. This signal is a discrete input to the K219 Exterior Lighting Control Module and M75 Windshield Wiper Motor. The K9 Body Control Module communicates with the M75 Windshield Wiper Motor via LIN, requesting wiping operation. As noted earlier, the second switch in the S82 Windshield Wiper/Washer Switch also pulls-down a signal circuit from the M75 Windshield Wiper Motor. This discrete signal indicates to the M75 Windshield Wiper Motor that high speed wiper operation has been selected. This secondary discrete circuit provides a redundant means of high speed wiper operation should a circuit fault occur on the signal circuit between the S82 Windshield Wiper/Washer Switch and K9 Body Control Module or CAN communication be interrupted between the K9 Body Control Module and K219 Exterior Lighting Control Module.

Mist (Single Wipe) Operation 

The K9 Body Control Module interprets the ignition being switched to ON and the K9 Body Control Module responds by sending a CAN message to the K219 Exterior Lighting Control Module to supply B+ to the M75 Windshield Wiper Motor. The K219 Exterior Lighting Control Module controls the KR12B Windshield Wiper Relay by providing voltage to the coil side of the relay. This energizes the relay, closing the relay's high current switch, which supplies B+ to the M75 Windshield Wiper Motor. The mist (single wipe) position is a momentary switch position that will return the S82 Windshield Wiper/Washer Switch to the off position as soon as the switch is released. With the S82 Windshield Wiper/Washer Switch in the mist (single wipe) position, the discrete signal circuit to the K9 Body Control Module is pulled down through two resistors in a resistor ladder to a low reference provided by the K9 Body Control Module. The K9 Body Control Module interprets this specific voltage pull-down as a request for wiper activation. The K9 Body Control Module communicates with the M75 Windshield Wiper Motor via LIN, requesting consistent low speed wiping operation as long as the S82 Windshield Wiper/Washer Switch is held in the mist (single wipe) position. If the mist (single wipe) position is only briefly selected, the K9 Body Control Module will request only a single wipe.

Wiper Park Operation 

With the S82 Windshield Wiper/Washer Switch in the off position, the discrete signal circuit to the K9 Body Control Module is pulled down through one resistor in a resistor ladder to a low reference provided by the K9 Body Control Module. The K9 Body Control Module interprets this specific voltage pull-down as a request to stop wiper activation. The K9 Body Control Module communicates with the M75 Windshield Wiper Motor via LIN, requesting wiper operation stop. The M75 Windshield Wiper Motor will park the windshield wipers in their lowest position.

The windshield wiper system consists of the following electrical components:

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