Rear Window Defrost (EMTC)

When the rear window defrost switch (located in the HVAC module) is activated, the BCM grounds the control circuit to activate the rear window defrost relay (located in the BJB). When the rear window defrost is active from the switch, the rear window defrost grid is energized and the BCM supplies voltage to illuminate the rear window defrost switch status LED. The rear window defrost system may also be automatically activated as an extra load for accelerated engine warm-up, however the defrost switch status LED will remain off unless the defrost switch is activated.

The BCM deactivates the rear window defrost relay when one of these conditions is met:

• The rear window defrost switch is pressed when the feature is active.
• Ignition state is changed from ON to OFF.
• A predetermined timer completes.
• Battery voltage has dropped below a specified threshold (load management strategy).