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Home >> Cadillac >> 2024 >> LYRIQ Tech, AWD >> Repair and Diagnosis >> Body & Frame >> Fixed And MOVEABLE Windows >> Diagnostic Information and Procedures >> Windshield Defogger Malfunction >> Circuit/System Testing

Circuit/System Testing

  1. Ignition OFF and all vehicle systems OFF, disconnect the X1 electrical connector at the E49 Windshield Heating Grid. It may take up to 2 min for all vehicle systems to power down.
  2. Test for less than 10 Ω between the E49 Windshield Heating Grid ground circuit terminal 2 and ground.
    • If 10 Ω or greater 
    1. Ignition OFF.
    2. Test for less than 2 Ω in the ground circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, repair the open/high resistance in the ground connection.
    • Go to next step: If less than 10 Ω 
  3. Connect a test lamp between the control circuit terminal 1 and ground, ignition ON/Vehicle in Propulsion/RUN mode.
  4. Verify the test lamp does not turn ON and OFF when pressing the appropriate switch on the A26 Heater and Air Conditioning User Interface Control - Front
    • If the test lamp turns ON and OFF 

      Test or replace the E49 Windshield Heating Grid.

    • Go to next step: If the test lamp does not turn ON and OFF 
  5. Ignition OFF, connect the X1 electrical connector at the E49 Windshield Heating Grid. Disconnect the X2 harness connector at the X50A Engine Wiring Harness Junction Block, ignition ON.
  6. Verify the E49 Windshield Heating Grid is not activated.
    • If the E49 Windshield Heating Grid is activated 
    1. Ignition OFF, disconnect the X1 harness connector at the E49 Windshield Heating Grid, ignition ON.
    2. Test for less than 1 V between the E49 Windshield Heating Grid control circuit terminal 1 and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, test or replace the E49 Windshield Heating Grid.
    • Go to next step: If the E49 Windshield Heating Grid is not activated 
  7. Connect a 20 A fused jumper wire between the control circuit terminal 21 X2 and B+.
  8. Verify the E49 Windshield Heating Grid activates.
    • If the E49 Windshield Heating Grid does not activate 
    1. Ignition OFF, remove the jumper wire, disconnect the X1 harness connector at the E49 Windshield Heating Grid.
    2. Test for infinite resistance between the E49 Windshield Heating Grid control circuit terminal 1 and ground.
      • If less than Infinite resistance, repair the short to ground on the circuit.
      • Go to next step: If infinite resistance
    3. Test for less than 2 Ω in the control circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, all OK.
    • Go to next step: If the E49 Windshield Heating Grid activates 
  9. Test for less than 10 Ω between the X50A Engine Wiring Harness Junction Block ground circuit terminal 29 and ground.
    • If 10 Ω or greater 
    1. Ignition OFF.
    2. Test for less than 2 Ω in the ground circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, repair the open/high resistance in the ground connection.
    • Go to next step: If less than 10 Ω 
  10. Connect the X2 harness connector at the X50A Engine Wiring Harness Junction Block. Disconnect the X5 harness connector at the K219 Lighting Control Module, ignition ON.
  11. Verify the E49 Windshield Heating Grid is not activated.
    • If the E49 Windshield Heating Grid is activated 
    1. Ignition OFF, disconnect the X2 harness connector at the X50A Engine Wiring Harness Junction Block, ignition ON/Vehicle in Propulsion/RUN mode.
    2. Test for less than 1 V between the K219 Lighting Control Module control circuit terminal 22 X5 and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, test or replace the X50A Engine Wiring Harness Junction Block.
    • Go to next step: If the E49 Windshield Heating Grid is not activated 
  12. Connect a 3 A fused jumper wire between the control circuit terminal 22 X5 and B+.
  13. Verify the E49 Windshield Heating Grid activates.
    • If the E49 Windshield Heating Grid does not activate 
    1. Ignition OFF, remove the jumper wire, disconnect the X2 harness connector at the X50A Engine Wiring Harness Junction Block.
    2. Test for infinite resistance between the K219 Lighting Control Module control circuit terminal 22 X5 and ground.
      • If less than Infinite resistance, repair the short to ground on the circuit.
      • Go to next step: If infinite resistance
    3. Test for less than 2 Ω in the control circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the X50A Engine Wiring Harness Junction Block.
    • Go to next step: If the E49 Windshield Heating Grid activates 
  14. Replace the K219 Lighting Control Module.
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