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Circuit/System Testing

  1. Verify that a test lamp illuminates between the B+ circuit terminal A 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 X1 harness connectors at the generator and GBCM.
  3. Ignition ON, verify the scan tool ECM GEN-F Terminal Signal parameter is 0%.
    • If greater than the specified value, test the field duty cycle signal circuit terminal 2 X1 for a short to voltage. If the circuit tests normal, replace the ECM.
  4. Connect a test lamp between the field duty cycle signal circuit terminal 2 X1 of the generator harness and B+. Verify the scan tool ECM GEN-F Terminal Signal parameter is greater than 95%.
    • If less than the specified range, test the circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
  5. Reconnect the GBCM harness connector. Disconnect the test lamp.
  6. Ignition ON, verify the scan tool ECM GEN-F Terminal Signal parameter is 0%.
    • If greater than the specified value, replace the GBCM.
  7. Connect a test lamp between the field duty cycle circuit terminal 2 X1 of the generator harness and B+. Verify the scan tool ECM GEN-F Terminal Signal parameter is greater than 95%.
    • If less than the specified range, replace the GBCM.
  8. If all circuits test normal, test or replace the generator.
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