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.
Circuit/System Description
The rear window defogger switch and indicator is an integral component of the HVAC control module. When the rear window defogger switch is pressed, the HVAC control module responds by illuminating the defogger indicator and sending a serial data message indicating a defog request. This serial data message is received by the liftgate module (LGM). The LGM responds to the defog request by providing voltage to the rear window defogger grid. Pressing the rear window defogger switch again will turn off the indicator and send a serial data message indicating the defog deactivation command. The LGM responds by deactivating the defogger grid.
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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.