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

Glass, Frames and Mechanisms

Pinpoint Tests

Pinpoint Test I: 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 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). 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).

- 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 I: THE DEFROST SYSTEM WILL NOT SHUT OFF AUTOMATICALLY

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I1 CHECK CIRCUIT CRD06 (BN/YE) FOR A SHORT TO VOLTAGE


- Disconnect: Rear Window Defrost Relay.
- Disconnect: Rear Window Defrost Grid Power C402A.
- Ignition ON.
- Measure the voltage between rear window defrost grid power circuit (BK), 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 I2.

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I2 CHECK THE REAR WINDOW DEFROST RELAY


- Start the engine.
- NOTICE: Use the Flex Probe Kit for all test connections to prevent damage to the wiring terminals. Do not use the test lamp probe.
- Connect a 12-volt incandescent test lamp between rear window defrost relay socket pin 86, circuit CH122 (WH/OG) and rear window defrost relay socket pin 85.




- Does the test lamp illuminate?

Yes
GO to I3.

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

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I3 CHECK CIRCUIT CH122 (WH/OG) FOR A SHORT TO GROUND


- Ignition OFF.
- Disconnect: HVAC Module C228A (without Navigation) or C2356A (with Navigation).
- Start the engine.
- Measure the resistance between rear window defrost relay socket pin 86, circuit CH122 (WH/OG), harness side and ground.




- Is the resistance greater than 10,000 ohms?

Yes
GO to I4.

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

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I4 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.

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