HVAC Control Module

Rear Defrost Switch: The scan tool displays On/Off. When the rear window defogger switch is depressed, the scan tool displays will momentarily display On.

Liftgate Module (LGM)

Rear Defog Requested: The scan tool displays Yes/No. When the rear window defogger switch is depressed, the HVAC control module sends a class 2 message to the LGM to enable the rear window defogger. The LGM enables the rear window defogger, which the scan tool displays as Yes.