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Home >> GMC >> 2018 >> Acadia Denali, FWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 167 (Engine Controls And Fuel - 3.6L (LGX LF4) - DTC P0650 To DTC P3436 And Diagnostic Information And Procedures) >> Diagnostic Information and Procedures >> Fuel Injector Balance Test >> Circuit System Testing

Circuit System Testing

WARNING: This page is about a different car, the 2017 Cadillac ATS. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition ON.
  2. Command the Fuel Pump Enable ON with a scan tool.
  3. Verify the Fuel Pressure Sensor parameter is between 320-580 kPa (46-84 PSI) with the fuel pump running.
    • If within 320-580 kPa (46-84 PSI) 
    4. NOTE:

    The fuel pressure may vary slightly when the fuel pump stops operating. After the fuel pump stops operating, the fuel pressure should stabilize and remain constant.

  4. Verify the Fuel Pressure Sensor parameter does not decrease greater than 34 kPa (5 PSI) within 1 minute.
    • If less than the specified value 
  5. Engine idling.
  6. Verify the scan tool Fuel Rail Pressure Sensor parameter is between 1.9-5.0 MPa (276-725 PSI).
    • If between 1.9-5.0 MPa (276-725 PSI) 
    7. NOTE:

    The engine speed must be between 600-1, 000 RPM to perform this test.

  7. Select the scan tool Fuel Injector Balance function.
  8. Test a Q17 Fuel Injector.
  9. Record a fuel pressure drop value for each Q17 Fuel Injector.
  10. Add all of the individual pressure drop values except for the fuel injector suspected of being faulty. This is the total pressure drop.
  11. Divide the total pressure drop by the number of fuel injectors that were added together. This is the average pressure drop.
  12. Multiply the average pressure drop by 0.20 (20%). This is the acceptable variance from the average pressure drop.
  13. Verify the difference between any individual pressure drop and the average pressure drop is not greater than the acceptable variance.
    • If greater than the acceptable variance 

      Replace the Q17 Fuel Injector.

    • If within the acceptable variance 
  14. Perform Fuel Injector Circuit Diagnosis .
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