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Home >> Cadillac >> 2021 >> CT4 Sport, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 50 (Mirrors) >> Diagnostic Information and Procedures >> Heated Mirrors Malfunction >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2022 Cadillac CT4. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF and all vehicle systems OFF, disconnect the connector at the appropriate E17 Outside Rearview Mirror Glass:
    • E17D Outside Rearview Mirror Glass - Driver = X510
    • E17P Outside Rearview Mirror Glass - Passenger = X610
  2. Verify a test lamp illuminates between ground circuit terminal 5 and B+.
    • If test lamp does not illuminate 

      Repair the open/high resistance on the appropriate circuit or ground connection:

    • E17D Outside Rearview Mirror Glass - Driver = Circuit 2150
    • E17P Outside Rearview Mirror Glass - Passenger = Circuit 2250
    • Go to next step: If the test lamp illuminates 
  3. Engine running, connect a test lamp between the control circuit terminal 8 and the ground circuit terminal 5.
  4. Verify the test lamp turns ON when operating the rear defogger switch.
    • If the test lamp is always OFF 
    1. Ignition OFF, remove the test lamp, disconnect the appropriate connector at the S79 Door Switch Panel Control Module:
      • S79D Front Side Door Window Control Switch - Driver = X1 Connector
      • S79P Front Side Door Window Switch - Passenger
    2. Test the appropriate circuit for an open/high resistance:
      • S79D Front Side Door Window Control Switch - Driver = Circuit 606
      • S79P Front Side Door Window Switch - Passenger = Circuit 607
      • If an open/high resistance is found, repair the fault on the circuit or ground connection.
      • Go to next step: If an open/high resistance is not found.
    3. Replace the appropriate S79 Front Side Door Window Switch.
    • Go to next step: If the test lamp turns ON 
  5. Test or replace the E17 Outside Rearview Mirror Glass.