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

Glass, Frames and Mechanisms

Pinpoint Tests

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

The rear window defrost relay, located in the Battery Junction Box (BJB), receives power from circuit CBP45 (YE). When the rear window defrost switch (integral to the HVAC module) is pressed, the HVAC module grounds circuit CH122 (WH/OG) to activate the rear window defrost relay. When the rear window defrost relay is activated, power is sent from the rear window defrost relay to the rear window defrost grid through circuit CRD06 (BN/YE). The rear window defrost grid is grounded through circuit GD149 (BK/GY).

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.

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


- Disconnect: Rear Window Defrost Relay.
- Ignition ON.
- Measure the voltage between rear window defrost relay pin 87, circuit CRD06 (BN/YE), harness side and ground.




- Is any voltage present?

Yes
REPAIR the circuit. TEST the system for normal operation.

No
GO to K2.

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K2 CHECK HVAC MODULE OUTPUT


- Start the engine.
- Measure the resistance between rear window defrost relay pin 86, circuit CH122 (WH/OG) and ground.




- Is the resistance less than 60 ohms?

Yes
GO to K3.

No
GO to K4.

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


- Ignition OFF.
- Disconnect: HVAC Module - EATC C228B or HVAC Module - EMTC C2357A.
- Ignition ON.
- Measure the resistance between rear window defrost relay pin 86, circuit CH122 (WH/OG) and ground.




- Is the resistance less than 5 ohms?

Yes
REPAIR the circuit. TEST the system for normal operation.

No
INSTALL a new HVAC module. TEST the system for normal operation.

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K4 CHECK THE REAR WINDOW DEFROST RELAY


- Carry out the rear window defrost relay component test.

- Did the rear window defrost relay pass the component test?

Yes
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. TEST the system for normal operation.

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

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