Chevrolet Trax: Rear window defogger malfunction

Diagnostic Instructions

• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
• Review Strategy Based Diagnosis for an overview of the diagnostic approach.
• Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Diagnostic Fault Information

Circuit/System Description

Battery positive voltage is supplied through a 30A fuse in the underhood fuse block, to the rear defogger relay switched input. When the rear window defogger switch is pressed, The HVAC control module commands the rear window defogger system by supplying voltage to the rear defogger relay coil. The rear defogger relay is energized and the defogger indicator is illuminated. With the relay energized, battery positive voltage is allowed from the relay switched input through the switch contacts and out the relay switched output to the rear window defogger grid.

Reference Information

Schematic Reference

Defogger Schematics (Encore), Defogger Schematics (Trax)

Connector End View Reference

WIRING SYSTEMS AND POWER MANAGEMENT - COMPONENT CONNECTOR END VIEWS - INDEX - ENCORE WIRING SYSTEMS AND POWER MANAGEMENT - COMPONENT CONNECTOR END VIEWS - INDEX - TRAX

Description and Operation

Rear Window Defogger Description and Operation

Electrical Information Reference

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

1. Engine running.
2. Verify the E18 Rear Defogger Grid turns ON and OFF pressing the rear window defogger switch.

• If the E18 Rear Defogger Grid does not turn ON and OFF

Refer to Circuit/System Testing

• If the E18 Rear Defogger Grid turns ON and OFF

3. Verify the rear window defogger indicator turns ON and OFF when commanding the Illuminate All Indicators On and Off with a scan tool.

• If the rear window defogger indicator does not turn ON and OFF

Replace the K33 HVAC Control Module.

• If the rear window defogger indicator turns ON and OFF

4. All OK.

Circuit/System Testing

1. Ignition OFF, and all vehicle systems OFF. Disconnect the X1 and X2 harness connectors at the E18 Rear Defogger Grid. It may take up to 2 minutes for all vehicle systems to power down.
2. Test for less than 10 ohms between the ground circuit terminal 1 X2 and ground.

If 10 ohms or greater

1. Ignition OFF.
2. Test for less than 2 ohms in the ground circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, repair the open/high resistance in the ground connection.

If less than 10 ohms

3. Connect a test lamp between the control circuit terminal 1 X1 and ground, Engine Running.
4. Verify the test lamp does not turn ON and OFF pressing the rear window defogger switch.

• If the test lamp turns ON and OFF

Test or replace the E18 Rear Defogger Grid.

• If the test lamp does not turn ON and OFF

5. Ignition OFF, connect the X1 and X2 harness connectors at the E18 Rear Defogger Grid. Disconnect the X2 harness connector at the X50A Fuse Block-Underhood. It may take up to 2 minutes for all vehicle systems to power down.
6. Test for less than 10 ohms between the ground circuit terminal C5 and ground.

• If 10 ohms or greater

1. Ignition OFF.
2. Test for less than 2 ohms in the ground circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, repair the open/high resistance in the ground connection.
• If less than 10 ohms

7. Ignition ON
8. Verify the E18 Rear Defogger Grid is not activated.

If the E18 Rear Defogger Grid is activated

1. Ignition OFF, disconnect the X1 harness connector at the E18 Rear Defogger Grid, ignition ON.
2. Test for less than 1 V between the X50A Fuse Block-Underhood control circuit terminal A3 and ground.

• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V, test or replace the E18 Rear Defogger Grid.
• If the E18 Rear Defogger Grid is not activated

9. Connect a 30A fused jumper wire between the control circuit terminal A3 and B+.
10. Verify the E18 Rear Defogger Grid activates.

• If the E18 Rear Defogger Grid does not activate

1. Ignition OFF, remove the jumper wire, disconnect the X1 harness connector at the E18 Rear Defogger Grid, ignition ON.
2. Test for infinite resistance between the control circuit and ground.

• If less than Infinite resistance, repair the short to ground on the circuit.
• If infinite resistance

3. Test for less than 2 ohms in the control circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, test or replace the E18 Rear Defogger Grid.
• If the E18 Rear Defogger Grid activates

11. Ignition OFF, connect the X2 harness connector at the X50A Fuse Block-Underhood. Disconnect the X2 harness connector at the K33 HVAC Control Module, ignition ON.
12. Verify the E18 Rear Defogger Grid is not activated.

• If the E18 Rear Defogger Grid is activated

1. Ignition OFF, disconnect the X2 harness connector at the X50A Fuse Block-Underhood.
2. Test for less than 1 V between the K33 HVAC Control Module control circuit terminal 19 and ground.

• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V, replace the X50A Fuse Block-Underhood.
• If the E18 Rear Defogger Grid is not activated

13. Connect a 3 A fused jumper wire between the control circuit terminal 19 and B+.
14. Verify the E18 Rear Defogger Grid activates.

• If the E18 Rear Defogger Grid does not activate

1. Ignition OFF, remove the jumper wire, disconnect the X2 harness connector at the X50A Fuse Block-Underhood, ignition ON.
2. Test for Test for infinite resistance between the K33 HVAC Control Module control circuit terminal 19 and ground.

• If less than Infinite resistance, repair the short to ground on the circuit.
• If infinite resistance

3. Test for less than 2 ohms in the control circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the X50A Fuse Block-Underhood.
• If the E18 Rear Defogger Grid activates

15. Replace the K33 HVAC Control Module.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Front Compartment Fuse Block Replacement
• Liftgate Window Replacement
• Control Module References for HVAC control module replacement, programming and setup

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