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Home › Chevrolet › 2007 › Impala SS › Repair and Diagnosis › Electrical › Charging Systems › Battery, Charging System And Starting System › Diagnostic Information and Procedures › DTC P0621 › Circuit/System Testing

Circuit/System Testing

  1. Ignition OFF, disconnect the harness connector at the generator.
  2. Ignition ON, test for less than 1 volt between the generator turn on signal and ground.
    • If greater than the specified range, test the generator turn on signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.
  3. Engine Running, test for greater than 3.5 volts between the generator turn on signal and ground.
    • If less than the specified range, test the generator turn on signal circuit for a short to ground, an open or a high resistance. If the circuit tests normal, replace the ECM.
  4. If the circuit test normal during the Ignition ON / Run tests replace the generator.
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