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Circuit/System Testing

    NOTE:

    It may take up to 2 min for all vehicle systems to power down before an accurate ground or low reference circuit continuity test can be performed.

  1. Ignition/Vehicle & All vehicle systems Off
  2. Disconnect the electrical connector: X1 & X2 E18 Rear Defogger Grid
  3. Test for less than 10 Ω between the test points: Ground circuit terminal 1 X2 & Ground
    • If 10 Ω or greater 
    1. Disconnect Ground Connection
    2. Test for less than 2 Ω between the test points: Ground circuit terminal 1 X2 @ Component harness & Ground Connection
      • 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 
  4. Verify the fuse is not open: F12UA Fuse
    • If the fuse is open 
    1. Replace the component: F12UA Fuse
    2. Verify the fuse does not open.
      • If the fuse opens, test or replace the component: X50A Fuse Block - Underhood
      • If the fuse does not open, go to the next step.
    • If the fuse is not open 
  5. Connect a test lamp between the test points: Control circuit terminal 1 X1 & Ground circuit terminal 1 X2
  6. Ignition On/Vehicle In Service Mode
  7. Operate the component: Rear Defogger Switch Pressed

    Verify the test lamp does not turn On and Off.

    • If the test lamp turns On and Off 

      Test or replace the component: E18 Rear Defogger Grid

    • If the test lamp does not turn On and Off 
  8. Ignition/Vehicle Off
  9. Connect the electrical connector: X1 & X2 E18 Rear Defogger Grid
  10. Disconnect the electrical connector: X2 X50A Fuse Block - Underhood
  11. Ignition On/Vehicle In Service Mode
  12. Momentarily connect a 25 A fused jumper wire between the test points: Control circuit terminal A3 X2 & B+

    Verify the component turns On and Off when connecting and disconnecting the jumper wire: E18 Rear Defogger Grid

    • If the component does not turn On and Off 
    1. Ignition/Vehicle Off & Remove Jumper wire(s)
    2. Disconnect the electrical connector: X1 E18 Rear Defogger Grid
    3. Ignition On/Vehicle In Service Mode
    4. Test for less than 1 V between the test points: Control circuit terminal 1 X1 @ Component harness & Ground
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V
    5. Ignition/Vehicle Off
    6. Test for infinite resistance between the test points: Control circuit terminal 1 X1 @ Component harness & Ground
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance
    7. Test for less than 2 Ω between the test points: Control circuit terminal 1 X1 @ Component harness & Terminal A3 X2 @ Fuse Block Harness
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, test or replace the component: E18 Rear Defogger Grid
    • If the component turns On and Off 
  13. Ignition/Vehicle & All vehicle systems Off
  14. Verify the fuse is not open: F12UA Fuse
    • If the fuse is open 

      Test or replace the component: X50A Fuse Block - Underhood

    • If the fuse is not open 
  15. Test for less than 10 Ω between the test points: Ground circuit terminal C5 X2 & Ground
    • If 10 Ω or greater 
    1. Disconnect Ground Connection
    2. Test for less than 2 Ω between the test points: Ground circuit terminal C5 X2 & Ground Connection
      • 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 
  16. Connect the electrical connector: X2 X50A Fuse Block - Underhood
  17. Disconnect the electrical connector: X2 K33 HVAC Control Module
  18. Ignition On/Vehicle In Service Mode
  19. Momentarily connect a 3 A fused jumper wire between the test points: Control circuit terminal 19 X2 & B+

    Verify the component turns On and Off when connecting and disconnecting the jumper wire: E18 Rear Defogger Grid

    • If the component does not turn On and Off 
    1. Ignition/Vehicle Off & Remove Jumper wire(s)
    2. Disconnect the electrical connector: X2 X50A Fuse Block - Underhood
    3. Ignition On/Vehicle In Service Mode
    4. Test for less than 1 V between the test points: Control circuit terminal 19 X2 @ Control module harness & Ground
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V
    5. Ignition/Vehicle Off
    6. Test for infinite resistance between the test points: Control circuit terminal 19 X2 @ Control module harness & Ground
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance
    7. Test for less than 2 Ω between the test points: Control circuit terminal 19 X2 @ Control module harness & Terminal B1 X2 @ Fuse Block Harness
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, test or replace the component: X50A Fuse Block - Underhood
    • If the component turns On and Off 
  20. Replace the component: K33 HVAC Control Module
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