Vehicle: 2013 Buick Verano, L4-2.4L, Automatic Transmission/Transaxle

Mileage: 166,008 Miles

Problem: The customer’s concern was that the windshield wipers randomly turned on when the vehicle’s ignition switch was off. The secondary problem was that the battery would go dead overnight.

Case Details: The first thing the technician noticed was that the “intermittent position” on the wiper switch only worked intermittently. The low/high positions worked normally, but the wipers would not turn off when the switch was in the off position. When using the windshield washer, the wipers would stay on until you turned off the key.

He tried swapping the wiper motor and wiper switch and replaced the BCM. The problem remained. At that point, he called an ALLDATA Tech-Assist consultant.

The consultant’s advice was that since the BCM, wiper motor, and switch had already been replaced, and the problem happens with the ignition is both on and off, the focus should now shift toward:

• Signal integrity problems
• Relay control issues
• Low voltage or wake-up circuit faults
• Harness or wiring problems
• Unintended BCM inputs keeping the wiper system active

On this vehicle, the BCM controls wiper operation based on:

• Multifunction switch inputs
• Wiper park-switch feedback from the wiper motor
• Serial data wake-up activity
• Retained accessory power (RAP) logic

A false input or incorrect feedback signal can cause the BCM to keep commanding the wipers on even when the switch is in the off position. The fact the wipers continue running after washer activation until the key is turned off strongly suggests the BCM is not seeing a valid “park” or “off” signal.

The technician began checking the wiring for the park signal circuit to the BCM. He found a corroded LIN BUS wire in the front bumper harness.

Confirmed Repair: The technician spliced in a new wire and retested. The wipers worked normally and stayed switched off. Fixed!