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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 P129B or P129C >> Circuit/System Testing

Circuit/System Testing

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  1. Ignition Off, disconnect the connector at the K111 Fuel Pump Power Control Module.
  2. Verify a test lamp illuminates between ground circuit terminal 14 and B+
    • If the test lamp does not illuminate 

      Repair the open/high resistance on circuit 2550 or the ground connection.

    • Go to next step: If the test lamp illuminates 
  3. Ignition ON.
  4. Verify a test lamp Illuminates between B+ circuit terminal 46 and ground.
    • If the test lamp does not illuminate and the circuit fuse is good 
    1. Test circuit 2640 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 2640 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 K111 Fuel Pump Power Control Module.
    • Go to next step: If the test lamp illuminates 
  5. Verify voltage at B+ terminal 46 is within 1 V of the C1 Battery voltage.
    • If not the specified value 

      Repair the high resistance on circuit 2640.

    • Go to next step: If the specified value 
  6. Replace the K111 Fuel Pump Power Control Module.
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