Pinpoint Test K: The Defrost System Will Not Shut Off Automatically

Glass, Frames and Mechanisms

Pinpoint Test K: The Defrost System Will Not Shut Off Automatically

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 Front Controls Interface Module (FCIM)) is pressed, the FCIM (Front Controls Interface Module) sends the defrost request message to the HVAC module over the Controller Area Network (CAN). The HVAC module activates the rear window defrost relay by grounding the relay coil through circuit CH122 (WH/OG). 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 GD173 (BK).

- DTC B1C83:14 (Rear Defog Relay: Circuit Short to Ground or Open)- When the HVAC module senses an open or short to ground on the rear window defrost relay control circuit, this DTC will set.

This pinpoint test is intended to diagnose the following:

- Wiring, terminals or connectors

- Rear window defrost relay

- HVAC module

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

NOTICE: Use the correct probe adapter(s) from the Flex Probe Kit when making measurements. Failure to use the correct probe adapter(s) may damage the connector.

K1 CHECK CIRCUIT CRD06 (BN/YE) FOR A SHORT TO VOLTAGE

- Disconnect: Rear Window Defrost Relay.

- Disconnect: Rear Window Defrost Grid Power.

- Ignition ON.

- Measure the voltage between rear window defrost grid power, circuit CRD06 (BN/YE), harness side and ground.





Is any voltage present?

Yes
REPAIR circuit CRD06 (BN/YE) for a short to voltage. TEST the system for normal operation.

No
GO to K2.

K2 CHECK THE REAR WINDOW DEFROST RELAY

NOTICE: The following step uses a test light to simulate normal circuit loads. Use only the test lamp recommended in the Special Tools table at the beginning or equivalent. To avoid connector terminal damage, use the Flex Probe Kit for the test light probe connection to the vehicle. Do not use the test lamp probe directly on any connector.

- Start the engine.

- Connect a 12-volt incandescent test lamp between rear window defrost relay socket pin 1, circuit CH122 (WH/OG) and rear window defrost relay socket pin 2, circuit CBP43 (GY).





Does the test lamp illuminate?

Yes
GO to K3.

No
INSTALL a new rear window defrost relay. TEST the system for normal operation.

K3 CHECK CIRCUIT CH122 (WH/OG) FOR A SHORT TO GROUND

- Ignition OFF.

- Disconnect: HVAC Module- DATC (Dual Automatic Temperature Control) C228A or HVAC Module- EMTC (Electronic Manual Temperature Control) C2357.

- Start the engine.

- Measure the resistance between rear window defrost relay socket pin 1, circuit CH122 (WH/OG), harness side and ground.





Is the resistance greater than 10,000 ohms?

Yes
GO to K4.

No
REPAIR short to ground in circuit CH122 (WH/OG). TEST the system for normal operation.

K4 CHECK FOR CORRECT HVAC MODULE OPERATION

- Disconnect all HVAC module connectors.

- Check for:
- corrosion.

- pushed-out pins.


- Connect all HVAC module connectors and make sure they seat correctly.

- Operate the system and verify the concern is still present.

Is the concern still present?

Yes
INSTALL a new HVAC module. TEST the system for normal operation.

No
The system is operating correctly at this time. Concern may have been caused by a loose or corroded connector. TEST the system for normal operation.