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
When the engine is running and the rear window defrost switch (integral to the Front Controls Interface Module (FCIM)) is pressed, the FCIM (Front Controls Interface Module) sends the defrost request message to the Instrument Panel Cluster (IPC) over the Infotainment Controller Area Network (I-CAN). The IPC (Instrument Panel Cluster) then sends the defrost request message to the Body Control Module (BCM) over the High Speed Controller Area Network (HS-CAN). The BCM (Body Control Module) then sends the defrost request message to the HVAC module through the Medium Speed Controller Area Network (MS-CAN). When the HVAC module receives the rear window defrost request message, it activates the rear window defrost relay by grounding the relay coil. When the rear window defrost relay is activated, voltage is supplied from the rear window defrost relay to the rear window defrost grid.
- B1C83:11 (Rear Defog Relay: Circuit Short To Ground)- sets when the HVAC module senses a short to ground on the rear window defrost relay control circuit.
This pinpoint test is intended to diagnose the following:
- Rear window defrost relay
- Wiring, terminals or connectors
- 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.
K1 CHECK THE REAR WINDOW DEFROST GRID POWER CIRCUIT FOR A SHORT TO VOLTAGE
- Disconnect: Rear Window Defrost Relay.
- Disconnect: Rear Window Defrost Grid C402A.
- Ignition ON.
- Measure the voltage between rear window defrost grid C402A-1, circuit CRD06 (BN/YE), 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 K2.
K2 CHECK HVAC MODULE OUTPUT
NOTICE: The following step uses a test light to simulate normal circuit loads. Use only the test light recommended in the Special Tools table at the beginning. To avoid connector terminal damage, use the Flex Probe Kit for the test light probe connection to the vehicle. Do not use the test light probe directly on any connector.
- Start the engine.
- Connect a 12-volt incandescent test light between rear window defrost relay socket pin 1, circuit CH122 (WH/OG) and rear window defrost relay socket pin 2, circuit CBB93 (GY/BN).
Does the test light illuminate?
Yes
GO to K3.
No
INSTALL a new rear window defrost relay. TEST the system for normal operation.
K3 CHECK THE REAR WINDOW DEFROST RELAY CONTROL CIRCUIT FOR A SHORT TO GROUND
- Ignition OFF.
- Disconnect: HVAC Module- Electronic Manual Temperature Control (EMTC) C2357 or HVAC Module- Dual Automatic Temperature Control (DATC) C228A.
- Measure the resistance between rear window defrost relay pin 1, circuit CH122 (WH/OG) and ground.
Is the resistance greater than 10,000 ohms?
Yes
GO to K4.
No
REPAIR short to ground in circuit CH122 (WH/OG). TEST the system for normal operation.
K4 CHECK FOR CORRECT HVAC MODULE OPERATION
- Disconnect all HVAC module electrical connectors.
- Check for:
- corrosion.
- pushed-out pins.
- Connect all HVAC module electrical 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.