Test F: The Defrost System Is Inoperative
PINPOINT TEST F: THE DEFROST SYSTEM IS INOPERATIVEF1-F2:
F2-F5:
F5-F7:
F7-F9:
Normal Operation
Under normal operation, the heated backlight relay receives power from the central junction box (CJB) through circuit 185 (BK). When the rear window defrost switch is depressed on the temperature control module, a ground signal is sent to the instrument cluster module (ICM) through circuit 688 (GY/LB). When the ICM receives ground through circuit 688 (GY/LB), the ICM grounds circuit 1009 (OG/YE) to activate the heated backlight relay. Power is then sent to the rear window defrost grid through circuit 186 (BN/LB) from the heated backlight relay. The rear window defrost grid is grounded to the chassis through circuit 1205 (BK).
Possible Causes
- Inoperative ICM
- Inoperative EATC or climate control module
- Inoperative heated backlight relay
- Open in circuits 185 (BK), 688 (GY/LB), 1009 (OG/YE) or 1205 (BK)