Test M
PINPOINT TEST M: THE DEFROST SYSTEM IS INOPERATIVETest M1:
Test M2-M4:
Test M5-M7:
Normal Operation
Under normal operation the heated backlight relay receives power from circuit 185 (BK) and central junction box fuse 10 (10A). When the rear window defrost switch is depressed on the temperature control module, a message is sent to the instrument cluster module (ICM) through the multiplex link system. Once the ICM receives the message to turn on the rear window defrost 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 then receives ground through circuit 1205 (BK) to chassis ground.
Possible Causes
- Inoperative ICM.
- Inoperative temperature control module.
- Inoperative heated backlight relay.
- Multiplex communication error.
- Open in circuits 185 (BK), 186 (BN/LB), 1009 (OG/YE), or 1205 (BK).