Test F: The Defrost System Will Not Shut Off Automatically

PINPOINT TEST F: THE DEFROST SYSTEM WILL NOT SHUT OFF AUTOMATICALLY

F1:

F2:

F3-F4:

F4 Continued:

Normal Operation
The heated rear window is controlled by the electronic automatic temperature control (EATC). The ignition switch must be in RUN for the EATC to operate. When the rear window defrost button is pressed, the EATC provides a ground for the heated rear window relay coil through circuit 688 (GY/LB). The heated rear window relay coil is energized, providing battery voltage to the antenna module on circuit 186 (BN/LB). The antenna module then supplies voltage and ground to the heated rear window grid.

Possible Causes
- Circuit 186 (BN/LB) short to voltage
- Circuit 688 (GY/LB) short to ground
- Heated rear window relay
- EATC
- Central junction box (CJB)