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HOMESERVICE MANUALSGMC2009CANYON 4D PICKUP, 2.9 9REPAIR AND DIAGNOSISENGINE MECHANICALSTARTERBATTERY, CHARGING SYSTEM AND STARTING SYSTEMDIAGNOSTIC INFORMATION AND PROCEDURESDTC B1492CIRCUIT/SYSTEM TESTING
2009 GMC Canyon 4D Pickup, 2.9 9

Circuit/System Testing

2009 GMC Canyon 4D Pickup, 2.9 9SECTION Circuit/System Testing

ECM Field Duty Cycle Signal Circuit Malfunction 

  1. Ignition OFF, disconnect the X1 harness connectors at the generator and GBCM.
  2. Ignition ON, verify the scan tool ECM GEN-F Terminal Signal parameter is 0 percent.
    • 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.
  3. 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 percent.
    • 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.
  4. Reconnect the GBCM harness connector. Disconnect the test lamp.
  5. Ignition ON, verify the scan tool ECM GEN-F Terminal Signal parameter is 0 percent.
    • If greater than the specified value, replace the GBCM.
  6. 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 percent.
    • If less than the specified range, replace the GBCM.
  7. If the circuit tests normal, replace the generator.

GBCM Field Duty Cycle Signal Circuit Malfunction 

  1. Ignition OFF, disconnect the GBCM harness connector.
  2. Ignition ON, verify the scan tool ECM GEN-F Terminal Signal parameter is 0 percent.
    • If greater than the specified value, test the field duty cycle signal circuit terminal B for a short to voltage.
  3. Connect a test lamp between the field duty cycle signal circuit terminal B and B+. Verify the scan tool ECM GEN-F Terminal Signal parameter is greater than 95 percent.
    • If less than the specified range, test the circuit for a short to ground or an open/high resistance.
  4. If the circuit tests normal, replace the GBCM.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.