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Circuit/System Testing

Both Outside Heated Mirrors Inoperative

  1. Vehicle OFF and all vehicle systems OFF, disconnect the KR4B Outside Rearview 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. Vehicle in Service Mode.
  4. Verify a test lamp illuminates between the B+ circuit terminal 30 and ground.
    • If the test lamp does not illuminate 
    • Replace the X50A Fuse Block-Underhood
    • If the test lamp illuminates 
  5. Connect a test lamp between the control circuit terminal 85 and the ground circuit terminal 86.
  6. Verify the test lamp turns ON and OFF when pressing the rear window defogger switch.
    • If the test lamp is always OFF 
    1. Vehicle OFF, remove the test lamp, 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, remove the test lamp, disconnect the harness connector at the K33 HVAC Control Module, Vehicle in Service Mode.
    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 K9 Body Control Module.
    • If the test lamp turns ON and OFF 
  7. Vehicle in Service Mode, connect a 10 A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87A.
  8. Verify both E17 Outside Rearview Mirror Glass are activated.
    • If both E17 Outside Rearview Mirror Glass do not activate 
    1. Vehicle OFF, remove the jumper wire, disconnect the X1 harness connector at the E17D Outside Rearview Mirror Glass-Driver and the E17P Outside Rearview Mirror Glass-Passenger.
    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 appropriate E17 Outside Rearview Mirror Glass.
    • If both E17 Outside Rearview Mirror Glass activates 
  9. Test or replace the KR4B Outside Rearview Mirror Heater Relay.

Single Outside Heated Mirror Inoperative

  1. Vehicle OFF, disconnect the X1 and X2 harness connectors at the appropriate E17 Outside Rearview Mirror Glass. 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 1 X2 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. Vehicle in Service Mode, connect a test lamp between the control circuit terminal 1 X1 and the ground circuit terminal 1 X2.
  4. Verify the test lamp turns ON and OFF when commanding the Rear Defogger On and Off with a scan tool.
    • If the test lamp is always OFF 
    1. Vehicle OFF, remove the test lamp, disconnect the KR4B Outside Rearview Mirror Heater Relay.
    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 E17 Outside Rearview Mirror Glass.
    • If the test lamp is always ON 
    1. Vehicle OFF, remove the test lamp, disconnect KR4B Outside Rearview Mirror Heater Relay, Vehicle in Service Mode.
    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, test or replace the KR4B Outside Rearview Mirror Heater Relay
    • If the test lamp turns ON and OFF 
  5. Test or replace the E17 Outside Rearview Mirror Glass.
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