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Home >> Cadillac >> 2017 >> CT6 Plug-In >> Repair and Diagnosis >> Body & Frame >> Fixed And MOVEABLE Windows >> Diagnostic Information and Procedures >> Rear Window Defogger Malfunction >> Circuit/System Testing
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Circuit/System Testing

  1. Ignition/Vehicle & All vehicle systems» Off
    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.
  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. Ground Connection» Disconnect
    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: F26RA Fuse/F28RA Fuse
    • If the fuse is open 
    1. Replace the component: F26RA Fuse/F28RA Fuse
    2. Verify the fuse does not open.
      • If the fuse opens» Test or replace the component: X53A Fuse Block - Rear Body
      • 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 @ X53A Fuse Block - Rear Body
  11. Ignition» On / Vehicle» In Service Mode
  12. Momentarily connect a 40 A fused jumper wire between the test points:
    • {Without UKL} Control circuit terminal 24 X2 & B+
    • {With UKL} Control circuit terminal 22 X2 & B+
  13. 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 open/high resistance in 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:
      • {Without UKL} Control circuit terminal 1 X1 @ Component harness & Control circuit terminal 24 X2 @ Fuse Block Harness
      • {With UKL} Control circuit terminal 1 X1 @ Component harness & Control circuit terminal 22 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 
  14. Ignition/Vehicle & All vehicle systems» Off
  15. Verify the fuse is not open: F26RA Fuse/F28RA Fuse
    • If the fuse is open 

      Test or replace the component: X53A Fuse Block - Rear Body

    • If the fuse is not open 
  16. Disconnect the electrical connector: X1 @ X53A Fuse Block - Rear Body
  17. Test for less than 10 Ω between the test points: Ground circuit terminal 27 X1 & Ground
    • If 10 Ω or greater 
    1. Ground Connection» Disconnect
    2. Test for less than 2 Ω between the test points: Ground circuit terminal 27 X1 & 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 
  18. Connect the electrical connector: X1 & X2 @ X53A Fuse Block - Rear Body
  19. Disconnect the electrical connector: X2 @ K33 HVAC Control Module
  20. Ignition» On / Vehicle» In Service Mode
  21. 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 @ X53A Fuse Block - Rear Body
    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:
      • {Without UKL} Control circuit terminal 19 X2 @ Control module harness & Terminal 34 X2 @ Fuse Block Harness
      • {With UKL} Control circuit terminal 19 X2 @ Control module harness & Terminal 15 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: X53A Fuse Block - Rear Body
    • If the component turns On and Off 
  22. Replace the K33 HVAC Control Module.
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