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Home › Buick › 2021 › Envision Essence, AWD › Repair and Diagnosis › Body & Frame › Fixed And MOVEABLE Windows › Diagnostic Information and Procedures › Rear Window Defogger Malfunction › Circuit/System Testing

Circuit/System Testing

  1. Ignition OFF and all vehicle systems OFF, disconnect the KR5 Rear Window Defogger Relay.
  2. Verify a test lamp illuminates between ground circuit terminal 86 and B+.
    • If the test lamp does not illuminate 
    1. Repair the open/high resistance on circuit 1150 or the ground connection.
    • Go to next step: If the test lamp illuminates 
  3. Engine Running.
  4. Verify a test lamp illuminates between the B+ circuit terminal 30 and ground.
    • If the test lamp does not illuminate 

      Replace the X50A Engine Wiring Harness Junction Block

    • Go to next step: If the test lamp illuminates 
  5. Connect a test lamp between the test points: Control circuit terminal 85 & ground
  6. Operate the component: rear window defogger switch - Pressed

    Verify the test lamp turns ON and OFF

    • If the test lamp is always OFF 
    1. Ignition OFF, remove the test lamp, disconnect the harness connector at the K9 Body Control Module
    2. Test for infinite resistance between the control 193 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 193 end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the K9 Body Control Module
    • If the test lamp is always ON 
    1. Ignition OFF, remove the test lamp, disconnect the harness connector at the K9 Body Control Module.
    2. Test for less than 1 V between the control 193 and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the K9 Body Control Module
    • Go to next step: If the test lamp turns ON and OFF 
  7. Ignition OFF and all vehicle systems OFF, connect the KR5 Rear Window Defogger Relay and disconnect the X2 harness connector at the E18 Rear Window Defogger Grid
  8. Verify a test lamp illuminates between ground circuit terminal 1 X2 and B+.
    • If the test lamp does not illuminate 
    1. Repair the open/high resistance on circuit 2950 or the ground connection.
    • Go to next step: If the test lamp illuminates 
  9. Disconnect the X1 harness connector at the E18 Rear Window Defogger Grid
  10. Connect a test lamp between the control circuit terminal 1 X1 and ground.
  11. Engine Running.
  12. Verify the test lamp turns ON and OFF when pressing the rear window defogger switch.
    1. Ignition OFF, remove the test lamp, disconnect the KR5 Rear Window Defogger Relay
    2. Test for infinite resistance between the control 293 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 293 end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the KR5 Rear Window Defogger Relay
    • If the test lamp is always ON 
    1. Ignition OFF, remove the test lamp, disconnect the harness connector at the KR5 Rear Window Defogger Relay.
    2. Test for less than 1 V between the control 293 and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the KR5 Rear Window Defogger Relay
    • Go to next step: If the test lamp turns ON and OFF 
  13. Test or replace the E18 Rear Window Defogger Grid
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