Test F: The Defrost System Is Inoperative
PINPOINT TEST F: THE DEFROST SYSTEM IS INOPERATIVEF1-F2:
F2-F4:
F4-F7:
F7 Continued:
Normal Operation
The heated backlight relay, which is integral to the smart junction box (SJB), receives power from circuit 1846 (GY/LB). When the rear window defrost switch is pressed on the electronic automatic temperature control (EATC) or electronic manual temperature control module (EMTC) control unit, a message is sent to the SJB through circuit 1426 (PK). Once the SJB receives the message to turn on the rear window defrost, the SJB grounds the heated backlight relay coil, which sends power to the rear window defrost grid through circuit 186 (BN/LB) from the SJB. The rear window defrost grid uses circuit 1205 (BK) for ground.
Possible Causes
- Inoperative SJB
- Inoperative EATC or EMTC
- Open in circuits 1846 (GY/LB), 1426 (PK), 1205 (BK) or 186 (BN/LB)
- Fuse