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ECM Signal Circuit Malfunction

  1. Verify that a test lamp illuminates between the B+ circuit ring 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 connector at the generator, and the harness connector at the GBCM.
  3. Ignition ON, verify the scan tool ECM GEN-F Terminal Signal is less than 5%.
    • If greater than the specified range, test the signal circuit terminal 2 X1 for a short to voltage. If the circuit tests normal, replace the ECM.
  4. Install a 3 A fused jumper wire between the signal circuit terminal 2 X1 and B+. Verify the scan tool ECM GEN-F Terminal Signal is greater than 95%.
    • If less than the specified range, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
  5. Ignition OFF, Reconnect the harness connector at the GBCM. Remove the jumper wire from the generator harness connector.
  6. Ignition ON, verify the scan tool ECM GEN-F Terminal Signal is less than 5%.
    • If greater than the specified range, replace the GBCM.
  7. Install a 3 A fused jumper wire between the signal circuit terminal 2 X1 and B+. Verify the scan tool ECM GEN-F Terminal Signal 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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