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). When the rear window defrost relay is active, the rear window defrost grid will be energized and the rear window defrost status LED will be illuminated. For vehicles equipped with a power sliding rear window, the rear window defrost relay will not activate the rear defrost relay unless the rear sliding window glass is in the fully CLOSED position due to a glass position switch in series with 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). Voltage is supplied to the rear window defrost relay through circuits SBB32 (VT/RD) and CBP43 (GY). 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 (BK).
This pinpoint test is intended to diagnose the following:
- Fuse(s)
- Rear window defrost relay
- Wiring, terminals or connectors
- Rear sliding glass position switch (if equipped)
- Rear window defrost grid
- HVAC module
- FCIM
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 (Passenger side terminal).
- Start the engine.
- Activate the rear window defrost switch and measure the voltage between rear window defrost grid power terminal, 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 (driver side terminal).
- Measure the resistance between rear window defrost grid ground terminal, harness side and ground.
- Is the resistance less than 5 ohms?
Yes
INSTALL a new rear window glass assembly. REFER to Window Glass - Rear Window Glass - Rear. TEST the system for normal operation.
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), harness side and ground; and between pin 3, circuit SBB32 (VT/RD), harness side and ground.
- Is the voltage greater than 10 volts for both measurements?
Yes
GO to H4.
No
VERIFY Battery Junction Box (BJB) fuse 32 (40A) and Smart Junction Box (SJB) fuse 43 (10A) are OK. If OK, REPAIR the circuit(s). 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. 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.
- If equipped, make sure the rear sliding glass is in the fully CLOSED position.
- Start the engine.
- Activate the rear window defrost switch.
- Connect the 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.
- 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
- Ignition OFF.
- 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). TEST the system for normal operation.
No
INSTALL a new rear window defrost relay. 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. TEST the system for normal operation.
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H7 CHECK CIRCUIT CH122 (WH/OG) FOR AN OPEN
- If equipped, make sure the rear sliding glass is in the fully CLOSED position.
- Ignition OFF.
- Disconnect: HVAC Module - DATC C228A (with navigation) or C2109A (without navigation) or HVAC Module - EMTC C294A.
- For vehicles equipped with Electronic Manual Temperature Control (EMTC), measure the resistance between rear window defrost relay socket pin 2, circuit CH122 (WH/OG), harness side and HVAC module - EMTC C294A-25, HVAC module - Dual Automatic Temperature Control (DATC) C2109A-25 (without navigation) or HVAC module - DATC C228A-12 (with navigation), circuit CH122 (WH/OG), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to H9.
No
If vehicle is equipped with a fixed rear window glass assembly, REPAIR the circuit. TEST the system for normal operation.
If vehicle is equipped with a power sliding rear window, GO to H8.
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H8 CHECK THE REAR SLIDING GLASS POSITION SWITCH
- Ignition OFF.
- Disconnect: Rear Window Defrost Grid In-Line Connector C3368.
- With the rear sliding window glass in the fully CLOSED position, measure the resistance between rear window defrost grid in-line C3368-3, circuit CH122 (WH/OG), harness side and rear window defrost grid in-line C3368-4, circuit CH122 (WH/OG), harness side.
- Is the resistance less than 5 ohms?
Yes
REPAIR the open circuit. TEST the system for normal operation.
No
INSPECT the wiring harness for any damage between the rear window defrost grid in-line connector and the rear window glass assembly. If the harness is OK, INSTALL a new rear window glass assembly. REFER to Window Glass - Rear Window Glass - Rear. TEST the system for normal operation.
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H9 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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