Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Rear Window Defrost
When the rear window defrost switch (part of the FCIM-B (Front Controls Interface Module "B")) is activated, a message is sent to the GWM through the HS-CAN3. From there, the message is sent to the HVAC module through the MS-CAN. When the HVAC module receives the request, it grounds the control circuit to activate the rear window defrost relay (located in the BJB). When the rear window defrost relay is activated, the rear window defrost grid is energized and heats the window glass.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.