Pinpoint Test L: The Defrost System LED Does Not Illuminate When the Defrost System is Active

Glass, Frames and Mechanisms

Pinpoint Test L: The Defrost System LED Does Not Illuminate When the Defrost System is Active

Refer to Wiring Diagram Set 100, Power Windows 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. The rear defrost self actuates when the ambient air temperature is less than 5° C (41° F) and engine coolant temperature is less than 60° C (140° F). The rear window defroster LED indicator does not illuminate when the rear defroster self actuates.

This pinpoint test is intended to diagnose the following:

- Wiring, terminals or connectors

- HVAC module

- BCM (Body Control Module)

PINPOINT TEST L : THE DEFROST SYSTEM LED DOES NOT ILLUMINATE WHEN THE DEFROST SYSTEM IS ACTIVE

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.

L1 CHECK FOR VOLTAGE SIGNAL TO THE REAR WINDOW DEFROST SWITCH LED

- Ignition OFF.

- Disconnect: HVAC Module C228A.

- Start the engine.

- Momentarily connect a fused jumper wire between HVAC module C228A-13, circuit GD115 (BK/GY), harness side and HVAC module C228A-16, circuit CRD09 (BU/GY), harness side.





- Remove the fused jumper wire.

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





Is the voltage greater than 10 volts?

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

No
GO to L2.

L2 CHECK THE REAR WINDOW DEFROST SWITCH LED CIRCUIT FOR AN OPEN OR SHORT TO GROUND

- Ignition OFF.

- Disconnect: BCM (Body Control Module) C2280F.

- Measure the resistance between HVAC module C228A-15, circuit CRD04 (BN/GN), harness side and BCM (Body Control Module) C2280F-11, circuit CRD04 (BN/GN), harness side; and between HVAC module C228A-15, circuit CRD04 (BN/GN), harness side and ground.





Is the resistance less than 5 ohms between the HVAC module and the BCM (Body Control Module) ; and greater than 10,000 ohms between the HVAC module and ground?

Yes
GO to L3.

No
REPAIR the circuit. TEST the system for normal operation.

L3 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.