Pinpoint Test H: The Defrost System is Inoperative

Glass, Frames and Mechanisms

Pinpoint Test H: The Defrost System is Inoperative

Refer to Wiring Diagram Set 56, Heated Window for schematic and connector information. Diagrams By Number

Normal Operation

When the engine is running and the defrost switch (integral to the HVAC module or Front Controls Interface Module (FCIM) if equipped with navigation system) is pressed, the HVAC module activates the rear window defrost relay by grounding the relay coil through circuit CH122 (WH/OG). For vehicles equipped with navigation system, the FCIM sends the defrost request message to the HVAC module over the Controller Area Network (CAN). Voltage is supplied to the rear window defrost relay through circuits SBB32 (VT/RD) and CBP43 (GY). When the defrost relay is activated, power is supplied from the relay to the rear window defrost grid through circuit CRD06 (BN/YE). Ground is supplied to the rear window defrost grid through circuit (BK).

- B1C83:11 Rear Defog Relay: Circuit Short to Ground - When the HVAC module senses a short to ground on the rear window defrost relay control circuit, this DTC will set.
- B1C83:13 Rear Defog Relay: Circuit Open - When the HVAC module senses an open on the rear window defrost relay control circuit, this DTC will set.

This pinpoint test is intended to diagnose the following:
- Fuse(s)
- Rear window defrost relay
- Wiring, terminals or connectors
- Rear window defrost grid
- HVAC module
- FCIM



PINPOINT TEST H: THE DEFROST SYSTEM IS INOPERATIVE

H1-H3:

H3-H4:

H4-H7:

H7-H8: