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Home >> Cadillac >> 2021 >> CT4 Sport, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 135 (12 V Starting And Charging - Diagnostic Information And Procedures) >> Diagnostic Information and Procedures >> DTC B19F4 >> Circuit/System Testing

Circuit/System Testing

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NOTE:
  • Use the schematics to verify the items listed below:
    • The control module's B+ and ground circuits.
    • The Control module Terminal numbers.
  • Some control module ground circuits may require up to 20 min after the ignition is turned Off before achieving a resistance reading of less than 5 Ω. In most cases the readings will drop below 20 Ω within 1 min indicating the control modules are going to sleep.
  1. Ignition Off, disconnect the connector at the appropriate control module.
  2. Verify a test lamp illuminates between each module ground circuit terminal and B+
    • If the test lamp does not illuminate 

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

    • Go to next step: If the test lamp illuminates 
  3. Ignition ON.
  4. Verify a test lamp Illuminates between modules B+ circuit terminal and ground.
    • If the test lamp does not illuminate and the circuit fuse is good 
    1. Test the B+ circuit 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 the B+ circuit 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 appropriate control module.
    • Go to next step: If the test lamp illuminates 
  5. Verify voltage at each B+ circuit terminal is within 1 V of the C1 Battery voltage.
    • If not the specified value 

      Repair the high resistance on the B+ circuit.

    • Go to next step: If the specified value 
  6. Ignition On
  7. Verify voltage at each control module ignition circuit terminal is within 1 V of the C1 Battery voltage.
    • If not the specified value 

      Repair the high resistance on the ignition circuit.

    • Go to next step: If the specified value 
  8. Replace the control module.
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