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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 985 (Instrument Panel System Displays & Gages) >> Diagnostic Information and Procedures >> Fuel Gage Inaccurate or Inoperative (Dual Tank) >> Circuit/System Testing

Circuit/System Testing

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  1. Ignition OFF, disconnect the harness connector at the primary and secondary fuel level sensors.
  2. Ignition OFF, test for less than 1.0 ohm between the primary fuel level sensor low reference circuit terminal B and ground.
    • If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
  3. Ignition OFF, test for less than 1.0 ohm between the secondary fuel level sensor low reference circuit terminal B and ground.
    • If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
  4. Jumper the primary fuel level sensor signal circuit terminal C to secondary fuel level sensor signal circuit terminal C. Install a Signal Generator and Instrument Panel Tester between the jumped signal circuits and ground.
  5. Ignition ON, vary the signal generator resistance between 40-250 ohms. Verify that the scan tool Fuel Tank Level Remaining parameter displays a range that varies between 5 and 95 percent as the signal generator resistance changes.
    • If not within the specified range, test both signal circuits for an open/high resistance. If the circuits test normal, replace the ECM.
  6. Vary the signal generator resistance between 40-250 ohms. Verify that the fuel gage displays a range that varies between empty and full as the signal generator resistance changes.
    • If the gage is incorrect, replace the IPC.
  7. If all circuits test normal, perform the fuel level sensor component test before replacing either the primary or secondary fuel level sensor.
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