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Home >> Cadillac >> 2021 >> CT4 Sport, RWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 135 (12 V Starting And Charging - Diagnostic Information And Procedures) >> Diagnostic Information and Procedures >> DTC P0621 >> Circuit/System Testing

Circuit/System Testing

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  1. Verify a test lamp illuminates between the G13 Generator B+ circuit terminal A X2 and ground.
    • If the test lamp does not illuminate and the circuit fuse is good 
    1. Test circuit 2 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 or high resistance is not found
    2. Verify the fuse is not open and there is voltage at the fuse.
    • If the test lamp does not illuminate and the circuit fuse is open 
    1. Test circuit 2 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. Replace the G13 Generator.
    • Go to next step: If the test lamp illuminates 
  2. Ignition Off, disconnect the X1 connector at the G13 Generator, engine running.
  3. Test for 1 V or greater between control circuit terminal 1 and ground.
    • If less than 1 V 
    1. Test circuit 25 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 25 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 or high resistance is not found
    3. Replace the K20 Engine Control Module.
    • Go to next step: If 1 V or greater 
  4. Ignition OFF, disconnect the appropriate connector at the K20 Engine Control Module.
  5. Ignition ON.
  6. Test for less than 1 V between control circuit terminal 1 at G13 Generator connector X1 and ground.
    • If greater than 1 V 

      Repair the short to voltage on circuit 25.

    • Go to next step: If 1 V or less 
  7. Replace the G13 Generator.