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Home >> Cadillac >> 2021 >> CT4 Sport, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 338 (Lighting System - Diagnostic Information And Procedures (2 Of 2)) >> Diagnostic Information and Procedures >> Headlamp Leveling Malfunction (Manual) >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2022 Cadillac CT5. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, exterior lamps OFF, disconnect the harness connector at the appropriate E13 Headlamp Assembly. It may take up to 2 min for all vehicle systems to power down.
  2. Test the appropriate circuit for an open/high resistance.
    • E13LA Headlamp Assembly - Left - 550
    • E13RA Headlamp Assembly - Right - 650
    • 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. Verify fuse F33DA is OK.
    • If fuse F33DA is open 
    1. Test circuit 539 for a short to ground.
      • If a short to ground is found, repair the fault on the circuit
      • Go to next step: If a short to ground is not found
    2. Test circuit 1839 for a short to ground.
      • If a short to ground is found, repair the fault on the circuit
      • Go to next step: If a short to ground is not found
    3. Replace the X51A Fuse Block - Instrument Panel.
    • Go to next step: If fuse F33DA is OK 
  4. Verify a test lamp illuminates between terminal 6 at the E13 Headlamp Assembly connector and ground.
    • If the test lamp does not illuminate 
    1. Test circuit 539 for an open/high resistance.
      • If an open/high resistance is found, repair the fault on the circuit
      • Go to next step: If an open/high resistance is not found
    2. Replace the X51A Fuse Block - Instrument Panel
    • Go to next step: If the test lamp does illuminates 
  5. Ignition OFF, disconnect the harness connector at the S42 Headlamp Leveling Switch.
  6. Test circuit 1350 for an open/high resistance
    • 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 
  7. Ignition ON, verify a test lamp illuminates between the circuit terminal 6 and ground.
    • If the test lamp does not illuminate 
    1. Test circuit 1839 for an open/high resistance.
      • If an open/high resistance is found, repair the fault.
      • Go to next step: If an open/high resistance is not found
    2. Replace the X51A Fuse Block - Instrument Panel
    • Go to next step: If the test lamp illuminates 
  8. Ignition OFF, connect the harness connector at the S42 Headlamp Leveling Switch.
  9. Ignition ON, test the voltage between the control terminal 8 at the E13 Headlamp Assembly harness connector and ground for each headlamp leveling switch position listed below.
    • Headlamp leveling switch position 0 - 10 V - 11 V
    • Headlamp leveling switch position 1 - 8.5 V - 9.9 V
    • Headlamp leveling switch position 2 - 8 V - 9 V
    • Headlamp leveling switch position 3 - 6 V - 7 V
    • If less than the specified voltage range for each headlamp leveling switch position 
    1. Ignition OFF, disconnect the harness connector at the S42 Headlamp Leveling Switch.
    2. Test circuit 189 for an open/high resistance.
      • If an open/high resistance is found, repair the fault.
      • Go to next step: If an open/high resistance is not found
    3. Replace the S42 Headlamp Leveling Switch
    • If greater than the specified voltage range for each headlamp leveling switch position 
    1. Ignition OFF, disconnect the harness connector at the S42 Headlamp Leveling Switch.
    2. Test circuit 189 for a short to voltage.
      • If a short to voltage is found, repair the fault.
      • Go to next step: If a short to voltage is not found
  10. Test or replace the E13 Headlamp Assembly.
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