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Circuit/System Testing

Upper Defogger Grid Inoperative

  1. Vehicle OFF, disconnect the KR5 rear defogger relay. It may take up to 2 minutes for all vehicle systems to power down.
  2. Test for less than 10 Ω between the ground circuit terminal 40 and ground.
    • If 10 Ω or greater 
    1. Vehicle 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.
    • If less than 10 Ω 
  3. Verify that a test lamp does not illuminate between the control circuit terminal 41 and ground.
    • If the test lamp illuminates 

      Repair the short to voltage on the control circuit

    • If the test lamp does not illuminate 
  4. Vehicle OFF, disconnect the X2 harness connector at the E18A rear defogger grid - upper. It may take up to 2 minutes for all vehicle systems to power down.
  5. Test for less than 10 Ω between the ground circuit terminal 1 and ground.
    • If 10 Ω or greater 
    1. Vehicle 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.
    • If less than 10 Ω 
  6. Connect the X2 harness connector at the E18A rear defogger grid - upper.
  7. Vehicle in Service Mode, connect a 40 A fused jumper wire between the B+ circuit terminal 43 and the control circuit terminal 42.
  8. Verify the E18A rear defogger grid - upper is activated.
    • If the E18A rear defogger grid - upper does not activate 
    1. Vehicle OFF, disconnect the X1 harness connector at the E18A rear defogger grid - upper.
    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 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 E18A rear defogger grid - upper.
    • If the E18A rear defogger grid - upper activates 
  9. Test or replace the KR5 rear defogger relay.

Lower Defogger Grid Inoperative

  1. Vehicle OFF, disconnect the KR4B outside rear view mirror heater relay. It may take up to 2 minutes for all vehicle systems to power down.
  2. Test for less than 10 Ω between the ground circuit terminal 86 and ground.
    • If 10 Ω or greater 
    1. Vehicle 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.
    • If less than 10 Ω 
  3. Verify that a test lamp does not illuminate between the control circuit terminal 87 and ground.
    • If the test lamp illuminates 

      Repair the short to voltage on the control circuit

    • If the test lamp does not illuminate 
  4. Vehicle OFF, disconnect the X1 harness connector at the E18B rear defogger grid - lower. It may take up to 2 minutes for all vehicle systems to power down.
  5. Test for less than 10 Ω between the ground circuit terminal A and ground.
    • If 10 Ω or greater 
    1. Vehicle 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.
    • If less than 10 Ω 
  6. Connect the X2 harness connector at the E18B rear defogger grid - lower.
  7. Vehicle in Service Mode, connect a 40 A fused jumper wire between the B+ circuit terminal 43 and the control circuit terminal 42.
  8. Verify the E18B rear defogger grid - lower is activated.
    • If the E18B rear defogger grid - lower does not activate 
    1. Vehicle OFF, disconnect the X2 harness connector at the E18B rear defogger grid - lower.
    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 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 E18B rear defogger grid - lower.
    • If the E18B rear defogger grid - lower activates 
  9. Test or replace the KR4B outside rear view mirror heater relay.

Rear Window Defogger System Inoperative

  1. Vehicle OFF, disconnect the KR5 rear defogger relay.
  2. Disconnect the KR4B outside rear view mirror heater relay.
  3. Connect a test lamp between the control circuit terminal 85 and the ground circuit terminal 86 at the KR4B outside rear view mirror heater relay, Vehicle ON.
  4. Verify the test lamp turns ON and OFF commanding the rear window defogger ON and OFF with a scan tool.
    • If the test lamp is always OFF 
    1. Vehicle OFF, disconnect the harness connector at the K33 HVAC control module.
    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 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 K33 HVAC control module.
    • If the test lamp is always ON 
    1. Vehicle OFF, disconnect the harness connector at the K33 HVAC control module, Vehicle ON.
    2. Test for less than 1 V between the control circuit and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the K33 HVAC control module.
    • If the test lamp turns ON and OFF 
  5. Test or replace the KR5 rear defogger relay or the KR4B outside rear view mirror heater relay.
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