Pinpoint Test D: The Defrost System Is Inoperative
Glass, Frames and Mechanisms
Pinpoint Tests
Pinpoint Test D: 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 rear window defrost switch on the HVAC module is pressed, a ground signal is sent to the Smart Junction Box (SJB) on circuit 1426 (PK). The SJB then grounds circuit 1389 (WH) which energizes the rear window defrost relay. When the rear window defrost relay is active, voltage is supplied to the rear window defrost grid through circuit 186 (BN/LB). The rear window defrost grid is grounded by circuit 1205 (BK). The SJB provides rear window defrost status to the HVAC module through circuit 1427 (TN/LB).
B1345-B2061:
This pinpoint test is intended to diagnose the following:
- Fuse(s)
- Wiring, terminals or connectors
- Rear window defrost relay
- HVAC module
- Rear window defrost grid
- SJB
PINPOINT TEST D: THE DEFROST SYSTEM IS INOPERATIVE
NOTICE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.
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D1 CHECK FOR RECORDED SJB DTCs
- Ignition ON.
- Check the recorded results from the SJB self-test.
- Are any DTCs retrieved?
Yes
If DTC B1348, GO to D10. If DTC B1349, GO to D9. If DTC B1345, GO to D13. If DTC B2060, GO to D16. If DTC B2061, GO to D15.
No
GO to D2.
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D2 CHECK CIRCUIT 1389 (WH) FOR GROUND
- Ignition OFF.
- Disconnect: Rear Window Defrost Relay.
- Ignition ON.
- Press the rear window defrost switch to ON.
- Measure the resistance between rear window defrost relay pin 86, circuit 1389 (WH), harness side and ground.
- Is the resistance less than 100 ohms?
Yes
GO to D3.
No
GO to D7.
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D3 CHECK CIRCUIT 298 (VT/OG) FOR AN OPEN
- Ignition OFF.
- Measure the voltage between rear window defrost relay pin 30, harness side and ground; and between rear window defrost relay pin 85, circuit 298 (VT/OG), harness side and ground.
- Is the voltage greater than 10 volts?
Yes
GO to D4.
No
VERIFY the Bussed Electrical Center (BEC) fuse 52 (30A) is 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.
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D4 CHECK THE REAR WINDOW DEFROST RELAY FOR AN OPEN OR INTERNAL SHORT (NO DTCs)
- Carry out the Rear Window Defrost Relay Component Test.
- Is the rear window defrost relay OK?
Yes
GO to D5.
No
INSTALL a new rear window defrost relay. TEST the system for normal operation.
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D5 CHECK CIRCUIT 186 (BN/LB) FOR AN OPEN
- Disconnect: Rear Window Defrost Grid C402A (coupe) or C402 (convertible).
- Ignition ON.
- Connect a fused jumper wire between rear window defrost relay pin 30, circuit 298 (VT/OG), harness side and rear window defrost relay pin 87, circuit 186 (BN/LB), harness side.
- Measure the voltage between rear window defrost grid C402a-1 (coupe), circuit 186 (BN/LB), harness side and ground; or between rear window defrost gridC402-1 (convertible), circuit 186 (BN/LB), harness side and ground.
- Is the voltage greater than 10 volts?
Yes
REMOVE the jumper wire. GO to D6 .
No
REPAIR the circuit. TEST the system for normal operation.
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D6 CHECK CIRCUIT 1205 (BK) FOR AN OPEN
- Disconnect: Rear Window Defrost Grid C402B (Coupe Only).
- Ignition OFF.
- Measure the resistance between rear window defrost grid C402B-1 (coupe), circuit 1205 (BK), harness side and ground; or between rear window defrost grid C402-2 (convertible), circuit 1205 (BK), harness side and ground.
- Is the resistance less than 5 ohms?
Yes
REPAIR the rear window defrost grid. 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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D7 CHECK THE HVAC FOR CORRECT OPERATION
NOTE: The use of an analog ohmmeter may be necessary for this step due to the momentary ground signal of the heated rear window switch.
- Ignition OFF.
- Disconnect: SJB C2280B.
- While pressing the rear window defrost switch to ON, measure the resistance between SJB C2280B-18, circuit 1426 (PK), harness side and ground.
- Is the resistance less than 5 ohms?
Yes
GO to D18.
No
GO to D8.
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D8 CHECK CIRCUIT 1426 (PK) FOR AN OPEN
- Disconnect: HVAC Module C294A.
- Measure the resistance between SJB C2280B-18, circuit 1426 (PK), harness side and HVAC C294A-10, circuit 1426 (PK), harness side.
- Is the resistance less than 5 ohms?
Yes
INSTALL a new HVAC module. TEST the system for normal operation.
No
REPAIR the circuit. TEST the system for normal operation.
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D9 CHECK CIRCUIT 298 (VT/OG) FOR VOLTAGE
- Ignition OFF.
- Disconnect: Rear Window Defrost Relay.
- Measure the voltage between rear window defrost relay pin 85, circuit 298 (VT/OG), harness side and ground.
- Is the voltage greater than 10 volts?
Yes
GO to D10.
No
VERIFY the BEC fuse 52 (30A) is 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.
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D10 CHECK THE REAR WINDOW DEFROST RELAY FOR AN OPEN OR AN INTERNAL SHORT (DTC B1348, B1349)
- Ignition OFF.
- Disconnect: Rear Window Defrost Relay.
- Carry out the Rear Window Defrost Relay Component Test.
- Is the rear window defrost relay OK?
Yes
GO to D11.
No
INSTALL a new rear window defrost relay. TEST the system for normal operation.
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D11 CHECK CIRCUIT 1389 (WH) FOR AN OPEN OR SHORT TO GROUND
- Disconnect: SJB C2280C.
- Measure the resistance between rear window defrost relay pin 86, circuit 1389 (WH), harness side and SJB C2280C-12, circuit 1389 (WH), harness side; and between rear window defrost relay pin 86, circuit 1389 (WH) and ground.
- Is the resistance less than 5 ohms between the rear window defrost relay and the SJB and greater than 10,000 ohms between rear window defrost relay and ground?
Yes
GO to D12.
No
REPAIR the circuit. TEST the system for normal operation.
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D12 CHECK CIRCUIT 1389 (WH) FOR A SHORT TO VOLTAGE
- Ignition ON.
- Measure the voltage between rear window defrost relay pin 86, circuit 1389 (WH), harness side and ground.
- Is any voltage present?
Yes
REPAIR the circuit. TEST the system for normal operation.
No
GO to D18.
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D13 VERIFY DTC B1345
- Ignition OFF.
- Disconnect: SJB C2280B.
- Ignition ON.
- Measure the resistance between SJB C2280B-18, circuit 1426 (PK), harness side and ground.
- Is the resistance greater than 10,000 ohms?
Yes
GO to D18.
No
GO to D14.
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D14 CHECK CIRCUIT 1426 (PK) FOR A SHORT TO GROUND
- Ignition OFF.
- Disconnect: HVAC Module C294A.
- Measure the resistance between SJB C2280B-18, circuit 1426 (PK), harness side and ground.
- Is the resistance greater than 10,000 ohms?
Yes
INSTALL a new HVAC module. TEST the system for normal operation.
No
REPAIR the circuit. TEST the system for normal operation.
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D15 CHECK CIRCUIT 1427 (TN/LB) FOR AN OPEN OR SHORT TO GROUND
- Ignition OFF.
- Disconnect: HVAC Module C294A.
- Disconnect: SJB C2280B.
- Measure the resistance between SJB C2280B-7, circuit 1427 (TN/LB), harness side and HVAC module C294A-4, circuit 1427 (TN/LB), harness side; and between SJB C2280B-7, circuit 1427 (TN/LB), harness side and ground.
- Is the resistance less than 5 ohms between the SJB and the HVAC and greater than 10,000 ohms between the SJB and ground?
Yes
GO to D16.
No
REPAIR the circuit. TEST the system for normal operation.
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D16 CHECK CIRCUIT 1427 (TN/LB) FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: HVAC Module C294A.
- Disconnect: SJB C2280B.
- Ignition ON.
- Measure the voltage between SJB C2280B-7, circuit 1427 (TN/LB), harness side and ground.
- Is any voltage present?
Yes
REPAIR the circuit. TEST the system for normal operation.
No
GO to D17.
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D17 CHECK THE HVAC MODULE FOR AN OPEN OR INTERNAL SHORT
- Install a known good HVAC module.
- Operate the rear window defrost.
- Does the indicator illuminate?
Yes
INSTALL a new HVAC module. TEST the system for normal operation.
No
GO to D18.
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D18 CHECK THE SJB FOR CORRECT OPERATION
- Disconnect all of the SJB connectors.
- Check for:
- corrosion.
- pushed-out pins.
- Connect all of the SJB 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 SJB. REPEAT the self-test. TEST the system for normal operation.
No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector.
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