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Home › Chevrolet › 2010 › Impala LTZ › Repair and Diagnosis › Electrical › Starter › Battery, Charging System And Starting System › Diagnostic Information and Procedures › DTC P0621 › Circuit/System Testing

Circuit/System Testing

  1. Verify that a test lamp illuminates between the generator B+ terminal 1 X2 and ground.
    • If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
  2. Ignition OFF, disconnect the harness connector at the generator.
  3. Ignition ON, test for less than 1 V between the generator turn ON control circuit X1 terminal 1 and ground.
    • If greater than the specified value, test the generator turn ON control circuit for a short to voltage. If the circuit tests normal, replace the ECM.
  4. Engine running, test for greater than 3.5 V between the generator turn ON control and ground.
    • If less than the specified value, test the generator turn on signal circuit for a short to ground, an open/high resistance. If the circuit tests normal, replace the ECM.
  5. If the circuit tests normal, test or replace the generator.
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