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.
HVAC Control Module
Rear Defog Output: The scan tool displays On/Off. When the rear window defogger switch is depressed, the HVAC control module energizes the Rear Window Defogger relay by grounding the control circuit of the relay, which the scan tool displays as On.
Rear Defrost Button: The scan tool displays On/Off. When the rear window defogger switch is depressed, the scan tool will momentarily display On.
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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.