Pinpoint Test H: The Defrost System Is Inoperative
Glass, Frames and Mechanisms
Pinpoint Tests
Pinpoint Test H: The Defrost System is Inoperative
Refer to Wiring Diagram Set 56, Heated Window for schematic and connector information. Diagrams By Number
Normal Operation
When the engine is running and the defrost switch (integral to the HVAC module or Front Controls Interface Module (FCIM), if equipped with navigation system) is pressed, the HVAC module activates the rear window defrost relay by grounding the relay coil through circuit CH122 (WH/OG). For vehicles equipped with navigation system, the FCIM sends the defrost request message to the HVAC module over the Controller Area Network (CAN). When the defrost relay is activated, power is supplied from the relay to the rear window defrost grid through circuit CRD06 (BN/YE). Ground is supplied to the rear window defrost grid through circuit GD173 (BK).
- DTC B1C83:12 (Rear Defog Relay: Circuit Short to Battery) - Sets when the HVAC module senses a short to voltage on the rear window defrost relay control circuit.
- DTC B1C83:14 (Rear Defog Relay: Circuit Short to Ground or Open) - Sets when the HVAC module senses an open or short to ground on the rear window defrost relay control circuit.
This pinpoint test is intended to diagnose the following:
- Fuse
- Rear window defrost relay
- Wiring, terminals or connectors
- HVAC module
- FCIM
- Rear window defrost grid
PINPOINT TEST H: THE DEFROST SYSTEM IS INOPERATIVE
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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H1 CHECK THE REAR WINDOW DEFROST GRID VOLTAGE
- Disconnect: Rear Window Defrost Grid Power.
- Start the engine.
- Activate the rear defrost switch and measure the voltage between rear window defrost grid power circuit (BK), harness side and ground.
- Is the voltage greater than 10 volts?
Yes
GO to H2.
No
GO to H3.
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H2 CHECK THE REAR WINDOW DEFROST GRID GROUND
- Ignition OFF.
- Disconnect: Rear Window Defrost Grid Ground C402B.
- Measure the resistance between rear window defrost grid ground C402B-1, circuit GD173 (BK) and ground.
- Is the resistance less than 5 ohms?
Yes
CARRY OUT the Grid Wire Test. REPAIR the rear window defrost grid or INSTALL a new rear window glass. REFER to Window Grid Wire Repair Window Grid Wire Repair. TEST the system for normal operation. Component Tests and General Diagnostics
No
REPAIR the circuit. TEST the system for normal operation.
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H3 CHECK THE POWER TO THE RELAY
- Ignition OFF.
- Disconnect: Rear Window Defrost Relay.
- Ignition ON.
- Measure the voltage between rear window defrost relay socket pin 1, circuit CBP43 (GY) and ground; and between rear window defrost relay socket pin 5, circuit SBB20 (GN/RD) and ground.
- Is the voltage greater than 10 volts?
Yes
GO to H4.
No
VERIFY Battery Junction Box (BJB) fuse 20 (40A) and Smart Junction Box (SJB) fuse 43 (10A) are OK. If OK, REPAIR the circuit. TEST the system for normal operation.
If not OK, REFER to the Wiring Diagrams to identify the possible causes of the circuit short. REPAIR the circuit. TEST the system for normal operation. Diagrams By Number
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H4 CHECK THE HVAC MODULE
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.
- Activate the rear window defrost switch.
- Connect a 12-volt incandescent test light between rear window defrost relay socket pin 2, circuit CH122 (WH/OG) and rear window defrost relay socket pin 1, circuit CBP43 (GY).
- Does the test light illuminate?
Yes
GO to H5.
No
If equipped with navigation system, GO to H6.
If not equipped with navigation system, GO to H7.
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H5 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
REPAIR open in circuit CRD06 (BN/YE). CLEAR the DTCs. TEST the system for normal operation.
No
INSTALL a new rear window defrost relay. CLEAR the DTCs. TEST the system for normal operation.
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H6 CHECK THE REAR WINDOW DEFROST SWITCH (CC_SW_R_DEF) PID
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: DataLogger - FCIM.
- Monitor the FCIM CC_SW_R_DEF PID while pressing and releasing the rear window defrost switch.
- Does the PID agree with the rear window defrost switch status?
Yes
GO to H7.
No
INSTALL a new FCIM. CLEAR the DTCs. TEST the system for normal operation.
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H7 CHECK CIRCUIT CH122 (WH/OG) FOR AN OPEN
- Ignition OFF.
- Disconnect: HVAC Module C228A (without navigation) or C2356A (with navigation).
- Measure the resistance between rear window defrost relay socket pin 2, circuit CH122 (WH/OG), harness side and HVAC module C228A-12 (without Navigation) or C2356A-12 (with Navigation), circuit CH122 (WH/OG), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to H8.
No
REPAIR the circuit. TEST the system for normal operation.
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H8 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.
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