Pinpoint Test H: The Defrost System is Inoperative
Glass, Frames and Mechanisms
Pinpoint Test H: The Defrost System is Inoperative
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. For vehicles equipped with navigation system, the FCIM (Front Controls Interface Module) sends the defrost request message to the HVAC module over the Controller Area Network (CAN). When the rear window defrost relay is active, voltage is supplied to the rear window defrost grid. For vehicles equipped with a power sliding rear window, the rear window defrost grid does not activate unless the rear sliding window glass is in the fully CLOSED position due to a glass position switch in series with the grid circuit. The glass position switch is integral to the power sliding rear window assembly. There is a feedback circuit incorporated into the glass position switch which illuminates the rear window defrost switch LED when the defrost grid is active and the sliding glass is fully closed. If the sliding glass is opened while the defrost system is active, the heated mirrors continue to operate and the rear window defrost switch LED is no longer illuminated.
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) (part of power sliding rear window assembly)
- Rear window defrost grid
- HVAC module
- FCIM (Front Controls Interface Module)
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.
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 H5.
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
If equipped with a power sliding rear window, GO to H3.
If not equipped with a power sliding rear window, INSTALL a new rear window glass assembly. REFER to Window Glass - Rear . TEST the system for normal operation.
No
REPAIR the circuit. TEST the system for normal operation.
H3 CHECK THE REAR WINDOW DEFROST SWITCH LED OPERATION
- Ignition OFF.
- Disconnect: Rear Window Defrost Grid Inline (Passenger Side) C3368.
- Install a fused jumper wire between rear window defrost grid inline C3368-1, circuit CH122 (WH/OG), harness side and C3368-2, circuit CRD06 (BN/YE), harness side.
- Start the engine.
- Activate the rear window defrost switch.
Does the rear window defrost switch LED illuminate?
Yes
INSTALL a new rear window glass assembly. REFER to Window Glass - Rear . TEST the system for normal operation.
No
GO to H4.
H4 CHECK THE REAR WINDOW DEFROST FEEDBACK CIRCUIT FOR AN OPEN
- Ignition OFF.
- Disconnect: HVAC Module- Dual Automatic Temperature Control (DATC) C228A (With Navigation) or C2109A (Without Navigation) or HVAC Module- Electronic Manual Temperature Control (EMTC) C294A.
- Measure the resistance between rear window defrost grid inline C3368 and the HVAC module.
- For vehicles equipped with EMTC (Electronic Manual Temperature Control), measure the resistance between rear window defrost grid inline C3368-1, circuit CH122 (WH/OG), harness side and HVAC module- EMTC (Electronic Manual Temperature Control) C294A-22, circuit CH122 (WH/OG), harness side.
- For vehicles equipped with DATC (Dual Automatic Temperature Control) (without navigation), measure the resistance between rear window defrost grid inline C3368-1, circuit CH122 (WH/OG), harness side and HVAC module- DATC (Dual Automatic Temperature Control) C2109A-22, circuit CH122 (WH/OG), harness side.
- For vehicles equipped with DATC (Dual Automatic Temperature Control) (with navigation), measure the resistance between rear window defrost grid inline C3368-1, circuit CH122 (WH/OG), harness side and HVAC module- DATC (Dual Automatic Temperature Control) C228A-9, circuit CH122 (WH/OG), harness side.
Is the resistance less than 5 ohms?
Yes
GO to H10.
No
REPAIR the circuit. TEST the system for normal operation.
H5 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 CBB54 (VT/OG), 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 H6.
No
VERIFY Battery Junction Box (BJB) fuse(s) 32 (40A) and 54 (5A) 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 [1][2]Diagrams By Number. REPAIR the circuit. TEST the system for normal operation.
H6 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 the 12-volt incandescent test light between rear window defrost relay socket pin 2, circuit CRD02 (BN/BU) and rear window defrost relay socket pin 1, circuit CBB54 (VT/OG).
Does the test light illuminate?
Yes
GO to H7.
No
If equipped with navigation system, GO to H8.
If not equipped with navigation system, GO to H9.
H7 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.
H8 CHECK THE REAR DEFROST SWITCH (CC_SW_R_DEF) PID
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: DataLogger- FCIM (Front Controls Interface Module).
- Monitor the FCIM (Front Controls Interface Module) CC_SW_R_DEF PID while pressing and releasing the rear window defrost switch.
Does the PID agree with the rear defrost switch status?
Yes
GO to H9.
No
INSTALL a new FCIM (Front Controls Interface Module). TEST the system for normal operation.
H9 CHECK THE REAR WINDOW DEFROST RELAY CONTROL CIRCUIT FOR AN OPEN
- Ignition OFF.
- Disconnect: HVAC Module- Dual Automatic Temperature Control (DATC) C228A (With Navigation) or C2109A (Without Navigation) or HVAC Module- Electronic Manual Temperature Control (EMTC) C294A.
- Measure the resistance between rear window defrost relay and the HVAC module.
- For vehicles equipped with EMTC (Electronic Manual Temperature Control), measure the resistance between rear window defrost relay socket pin 2, circuit CRD02 (BN/BU) and HVAC module- EMTC (Electronic Manual Temperature Control) C294A-25, circuit CRD02 (BN/BU), harness side.
- For vehicles equipped with DATC (Dual Automatic Temperature Control) (without navigation), measure the resistance between rear window defrost relay socket pin 2, circuit CRD02 (BN/BU) and HVAC module- Dual Automatic Temperature Control (DATC) C2109A-25, circuit CRD02 (BN/BU), harness side.
- For vehicles equipped with DATC (Dual Automatic Temperature Control) (with navigation), measure the resistance between rear window defrost relay socket pin 2, circuit CRD02 (BN/BU) and HVAC module- DATC (Dual Automatic Temperature Control) C228A-12, circuit CRD02 (BN/BU), harness side.
Is the resistance less than 5 ohms?
Yes
GO to H10.
No
REPAIR the circuit. TEST the system for normal operation.
H10 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.