Pinpoint Test J: The Defrost System Is Inoperative

WARNING: This page is about a different car, the 2014 Lincoln MKX and 2014 Ford Edge. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: 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.
  
  Fig 1: Measuring Voltage Between Antenna Module C4194B-1, Circuit CRD06 (BN/YE), Harness Side And Ground
  Courtesy of FORD MOTOR CO.

Is the voltage greater than 10 volts?

Yes : GO to J2 .
No : VERIFY BJB fuse 26 (40A) is OK. If OK, GO to J3.
If not OK, REFER to the SYSTEM WIRING DIAGRAMS to identify the possible causes of the circuit short. 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.
  
  Fig 2: Measuring Resistance Between High Mounted Stoplamp C475B-1, Circuit GD173 (BK), Harness Side And Ground
  Courtesy of FORD MOTOR CO.

Is the resistance less than 5 ohms?

Yes : CARRY OUT the GRID WIRE TEST . 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.
  
  Fig 3: Measuring Voltage Between Rear Window Defrost Relay Socket Pin 2, Circuit CBB93 (GY/BN) And Ground
  Courtesy of FORD MOTOR CO.

Is the voltage greater than 10 volts?

Yes : GO to J4 .
No : VERIFY BJB fuse 93 (5A) is OK. If OK, REPAIR the circuit in question. TEST the system for normal operation.
If not OK, REFER to the SYSTEM WIRING DIAGRAMS to identify the possible causes of the circuit short. REPAIR the circuit. TEST the system for normal operation.
J4 CHECK THE HVAC MODULE OUTPUT
NOTE: The following step uses a test light to simulate normal circuit loads. Use only the test light recommended in the SPECIAL TOOL DESCRIPTION . 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).
  
  Fig 4: Checking HVAC Module Output
  Courtesy of FORD MOTOR CO.

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.
  Refer to OEM WIRING DIAGRAMS COMPONENT TESTING .

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 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 . For additional information, REFER to INFORMATION AND ENTERTAINMENT SYSTEMS . 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 C2357-25 or HVAC module - DATC C228A-25 , circuit CH122 (WH/OG), harness side.
  
  Fig 5: Measuring Resistance Between Rear Window Defrost Relay Socket Pin 1, Circuit CH122 (WH/OG), And HVAC Module - EMTC C2357-25
  Courtesy of FORD MOTOR CO.

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. For additional information, refer to CLIMATE CONTROL . 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.