Test F: The Defrost System Is Inoperative

PINPOINT TEST F: THE DEFROST SYSTEM IS INOPERATIVE

Normal Operation
Under normal operation, the rear defrost relay receives power from the battery junction box (BJB) through circuit SBB15 (WH/RD).

For vehicles equipped with HVAC module - electronic automatic temperature control (EATC), when the rear window defrost switch is depressed, a message is sent to the smart junction box (SJB) through the controller area network (CAN). When the SJB receives a rear window defrost ON message through the CAN, the SJB starts an internal 10 minute timer and grounds the rear defrost relay coil, which activates the rear defrost relay. When the rear defrost relay is active, power is sent to the rear window defrost grid through circuit CRD06 (BN/YE) from the rear defrost relay. The rear window defrost grid is grounded to the chassis through circuit GD150 (BK/WH).

For vehicles equipped with HVAC module - electronic manual temperature control (EMTC), when the rear window defrost switch is depressed, a ground signal is sent to the SJB through circuit CRD09 (BU/GY). When the SJB receives ground through circuit CRD09 (BU/GY), the SJB starts an internal 10 minute timer and grounds the rear defrost relay coil, which activates the rear defrost relay. When the heated backlight relay is active, power is sent to the rear window defrost grid through circuit CRD06 (BN/YE) from the rear defrost relay. The rear window defrost grid is grounded to the chassis through circuit GD150 (BK/WH).

- DTC B1347 Heated Backlite Relay Circuit Failure - Open or short to ground in rear defrost relay coil circuit.

This pinpoint test is intended to diagnose the following:
- Fuse
- Inoperative rear defrost relay
- Wiring, terminals or connectors
- Inoperative SJB
- Inoperative HVAC module - EMTC or HVAC module - EATC

F1-F3:

F4-F7:

F8-F10: