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Home >> Cadillac >> 2021 >> CT4 Sport, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 224 (Lighting System - Diagnostic Information And Procedures (1 Of 2)) >> Diagnostic Information and Procedures >> DTC B100D >> Circuit/System Testing

Circuit/System Testing

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  1. Ignition OFF, disconnect the connector at the S36 Dimmer Switch, ignition ON.
  2. Verify a test lamp illuminates between low reference terminal 1 and B+.
    • If the test lamp does not illuminate 
    1. Test circuit 5005 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 K9 Body Control Module.
    • Go to next step: If the test lamp illuminates 
  3. Test for 4.8 V - 5.2 V between signal circuit terminal 2 and ground.
    • If less than 4.8 V 
    1. Test circuit 44 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 44 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.
    3. Replace the K9 Body Control Module.
    • If greater than 5.2 V 
    1. Test circuit 44 for a short to voltage.
      • If a short to voltage is found, repair the fault on the circuit.
      • Go to next step: If a short to voltage is not found.
    2. Replace the K9 Body Control Module.
    • Go to next step: If 4.8 V - 5.2 V 
  4. Replace the S36 Dimmer Switch.
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