Pinpoint Test I: The Defrost System Is Inoperative
Glass, Frames and Mechanisms
Pinpoint Tests
Pinpoint Test I: The Defrost System is Inoperative
Refer to Wiring Diagram Set 56, Heated Window for schematic and connector information. Diagrams By Number
Normal Operation
With the engine running, the HVAC module activates the rear window defrost relay by grounding the relay coil through circuit CH122 (WH/OG). 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 GD150 (BK/WH).
This pinpoint test is intended to diagnose the following:
- Fuse(s)
- Rear window defrost relay
- Wiring, terminals or connectors
- HVAC module
- Open or short in rear window defrost grid
PINPOINT TEST I: 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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I1 CHECK THE REAR WINDOW DEFROST GRID VOLTAGE
- Disconnect: Rear Window Defrost Grid Power C402A.
- Start the engine.
- Activate the rear defrost switch and measure the voltage between rear window defrost grid power C402A, circuit CRD06 (BN/YE) and ground.
- Is the voltage greater than 10 volts?
Yes
GO to I2.
No
GO to I3.
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I2 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, circuit GD150 (BK/WH) 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 Window Grid Wire Repair. TEST the system for normal operation.
No
REPAIR the circuit. TEST the system for normal operation.
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I3 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 CBB52 (GN/WH), harness side and pin 3, circuit SBB51 (BU/RD), harness side and ground.
- Is the voltage greater than 10 volts?
Yes
GO to I4.
No
VERIFY Battery Junction Box (BJB) fuse 51 (40A) and fuse 52 (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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I4 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. 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 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 CBB52 (GN/WH).
- Does the test light illuminate?
Yes
GO to I5.
No
GO to I6.
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I5 CHECK THE REAR WINDOW DEFROST RELAY
- Ignition OFF.
- Carry out the rear window defrost relay component test.
Refer to Wiring Diagrams for component testing. Diagrams By Number
- 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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I6 CHECK CIRCUIT CH122 (WH/OG) FOR AN OPEN
- Ignition OFF.
- Disconnect: HVAC Module - EATC C228B or HVAC Module - EMTC C2357B.
- Measure the resistance between rear window defrost relay socket pin 2, circuit CH122 (WH/OG), harness side and C228B-23 (HVAC module - Electronic Automatic Temperature Control (EATC)) or C2357B-23 (HVAC module - Electronic Manual Temperature Control (EMTC)) circuit CH122 (WH/OG), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to I7.
No
REPAIR the circuit. TEST the system for normal operation.
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I7 CHECK FOR CORRECT HVAC MODULE
- Disconnect all HVAC module connectors.
- Check for:
- corrosion.
- pushed-out pins.
- Connect all HVAC module 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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