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. Diagrams By Number
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 receives the defrost request signal, it supplies voltage to the rear window defrost grid. When the rear window defrost is active, the BCM 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
- HVAC module
- BCM
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.
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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.
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L2 CHECK THE REAR WINDOW DEFROST SWITCH LED CIRCUIT FOR AN OPEN OR SHORT TO GROUND
- Ignition OFF.
- Disconnect: BCM C2280F.
- Measure the resistance between HVAC module C228A-15, circuit CRD04 (BN/GN), harness side and BCM 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; 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.
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L3 CHECK FOR CORRECT BCM MODULE OPERATION
- Disconnect all the BCM connectors.
- Check for:
- corrosion.
- pushed-out pins.
- Connect all the BCM 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. REFER to Multifunction Electronic Modules Body Control Module (BCM). 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.
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