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 Electrical Diagrams.

Normal Operation

The engine must be running for the rear window defrost system to operate. When the rear window defrost switch (integral to the HVAC module) is pressed, a ground signal is sent to the Body Control Module (BCM). When the BCM (Body Control Module) receives the defrost request signal, it supplies voltage to the rear window defrost grid. When the rear window defrost is active, the BCM (Body Control Module) supplies voltage through a dedicated feedback circuit to the HVAC module to illuminate the LED indicator.

This pinpoint test is intended to diagnose the following:

- Wiring, terminals or connectors

- BCM (Body Control 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 FOR VOLTAGE TO THE REAR WINDOW DEFROST GRID WITH BCM (Body Control Module) DISCONNECTED

- Ignition OFF.

- Disconnect: BCM (Body Control Module) C2280C.

- Ignition ON.

- Measure the voltage between BCM (Body Control Module) C2280C-10, circuit CRD06 (BN/YE), harness side and ground.





Is any voltage present?

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

No
GO to K2.

K2 CHECK FOR A SHORT TO VOLTAGE ON THE SWITCH ILLUMINATION CIRCUIT

- Ignition OFF.

- Disconnect: BCM (Body Control Module) C2280F.

- Disconnect: HVAC Module C228A.

- Ignition ON.

- Measure the voltage between HVAC module C228A-15, circuit CRD04 (BN/GN), harness side and ground.





Is any voltage present?

Yes
REPAIR the short to voltage in circuit CRD04 (BN/GN). TEST the system for normal operation.

No
GO to K3.

K3 CHECK FOR CORRECT BCM (Body Control Module) MODULE OPERATION

- Disconnect all the BCM (Body Control Module) connectors.

- Check for:
- corrosion.

- pushed-out pins.


- Connect all the BCM (Body Control 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 BCM (Body Control Module). TEST the system for normal operation.

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