Pinpoint Test J: The Defrost System Is Inoperative
Glass, Frames and Mechanisms
Pinpoint Test J: The Defrost System is Inoperative
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.
- B1C83:13 (Rear Defog Relay: Circuit Open)- sets when the HVAC module senses an open on the rear window defrost relay control circuit.
This pinpoint test is intended to diagnose the following:
- Fuse(s)
- Rear window defrost relay
- Wiring, terminals or connectors
- Rear window defrost grid
- FCIM (Front Controls Interface Module)
- HVAC module
PINPOINT TEST J : 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.
J1 CHECK THE REAR WINDOW DEFROST GRID VOLTAGE
- Disconnect: Rear Window Defrost Grid C402A.
- Start the engine.
- Activate the rear window defrost switch and measure the voltage between rear window defrost grid C402A-1, circuit CRD06 (BN/YE), harness side and ground.
Is the voltage greater than 10 volts?
Yes
GO to J2.
No
VERIFY BJB (Battery Junction Box) fuse 26 (40A) is OK. If OK, GO to J3.
If not OK, REFER to the Wiring Diagrams to identify the possible causes of the circuit short Electrical Diagrams. REPAIR the circuit. TEST the system for normal operation.
J2 CHECK THE REAR WINDOW DEFROST GRID GROUND
- Ignition OFF.
- Disconnect: Rear Window Defrost Grid C402B.
- Measure the resistance between rear window defrost grid C402B-1, circuit GD149 (BK/GY), harness side and ground.
Is the resistance less than 5 ohms?
Yes
CARRY OUT the Grid Wire Test Component Tests and General Diagnostics. REPAIR the rear window defrost grid or INSTALL a new liftgate glass. REFER to Window Grid Wire Repair . TEST the system for normal operation.
No
REPAIR the circuit. TEST the system for normal operation.
J3 CHECK THE VOLTAGE SUPPLY TO THE REAR WINDOW DEFROST RELAY
- Ignition OFF.
- Disconnect: Rear Window Defrost Relay.
- Ignition ON.
- Measure the voltage between rear window defrost relay socket pin 2, circuit CBB93 (GY/BN) and ground; and between rear window defrost relay socket pin 3, circuit SBB26 (YE/RD) and ground.
Is the voltage greater than 10 volts?
Yes
GO to J4.
No
VERIFY BJB (Battery Junction Box) fuse 93 (5A) is OK. If OK, REPAIR the circuit in question. TEST the system for normal operation.
If not OK, REFER to the Wiring Diagrams to identify the possible causes of the circuit short Electrical Diagrams. REPAIR the circuit. TEST the system for normal operation.
J4 CHECK THE 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.
- Activate the rear window defrost switch.
- 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 J5.
No
GO to J6.
J5 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.
J6 CHECK THE REAR WINDOW DEFROST SWITCH (CC_SW_R_DEF) PID
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: DataLogger- Front Controls Interface Module (FCIM).
- 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 window defrost switch status?
Yes
GO to J7.
No
INSTALL a new FCIM (Front Controls Interface Module). TEST the system for normal operation.
J7 CHECK THE REAR WINDOW DEFROST RELAY CONTROL CIRCUIT FOR AN OPEN
- 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 socket pin 1, circuit CH122 (WH/OG), and HVAC module- EMTC (Electronic Manual Temperature Control) C2357-25 or HVAC module- DATC (Dual Automatic Temperature Control) C228A-25, circuit CH122 (WH/OG), harness side.
Is the resistance less than 5 ohms?
Yes
GO to J8.
No
REPAIR the circuit. TEST the system for normal operation.
J8 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.