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Home >> Buick >> 2015 >> Regal GS, AWD >> Repair and Diagnosis >> Engine Performance >> Testing & Diagnosis >> Engine Controls And Fuel - 2.0L (LTG) - DTC P0335 To DTC P2635 And Diagnostic Information And Procedures >> Diagnostic Information and Procedures >> Fuel System Diagnosis >> Circuit/System Verification

Circuit/System Verification

NOTE:
  • Repair all fuel system related DTCs, except P2635, before performing this diagnostic.
  • Inspect the fuel system for damage or external leaks before proceeding.
  • Verify that adequate fuel is in the fuel tank before proceeding.
  • The Fuel Pump Enable may need to be commanded ON a few times in order to obtain the highest possible fuel pressure.
  • DO NOT perform the Fuel System Diagnosis if the engine coolant temperature is above 60°C (150°F). High fuel pressure readings may result due to hot soak fuel boiling. With the engine OFF, the fuel pressure may increase beyond the pressure relief regulator valve's setting point of 690 kPa (100 psi) ±5 percent.
  1. Ignition ON, engine OFF, command the Fuel Pump Enable On several times with a scan tool.
  2. Verify the Fuel Pressure Sensor parameter is between 345-650 kPa (50-94 psi) with the fuel pump running.
    • If less than 345 kPa (50 psi) 

      Refer to Circuit/System Testing - Fuel Pressure Low.

    • If greater than 650 kPa (94 psi) 

      Replace the G12 Fuel Pump.

    • If between 345-650 kPa (50-94 psi) 
  3. Verify that the Fuel Pressure Sensor parameter, after the fuel pump is turned off, decreases to less than 600 kPa (87 psi).
    • If greater than 600 kPa (87 psi) 

      Replace the G12 Fuel Pump.

    • If less than 600 kPa (87 psi) 
  4. Verify that the Fuel Pressure Sensor parameter does not decrease greater than 34 kPa (5 psi) in 1 minute.
    • If greater than 34 kPa (5 psi) 

      Refer to Circuit/System Testing - Fuel Pressure Leaks Down.

    • If less than 34 kPa (5 psi) 
  5. Engine idling.
  6. Verify the Fuel Pressure Sensor parameter is between 300-400 kPa (43-58 psi).
    • If less than 300 kPa (43 psi) 

      Refer to Circuit/System Testing - Fuel Pressure Low.

    • If greater than 400 kPa (58 psi) 

      Replace the G12 Fuel Pump.

    • If between 300-400 kPa (43-58 psi) 
  7. Verify the scan tool Short Term Fuel Pump Trim and the Long Term Fuel Pump Trim when multiplied together are less than 1.5.
    • If greater than 1.5 

      Refer to Circuit/System Testing - Fuel Pressure Low.

    • If less than 1.5 
  8. Verify the scan tool Pressure Sensor and the Desired Fuel Pressure are within 45 kPa (6.5 psi) at 300 kPa (43.5 psi) request or 60 kPa (8.7 psi) at 400 kPa (58 psi) request of each other while operating the vehicle through varying loads.
    • If greater than 45 kPa (6.5 psi)/60 kPa (8.7 psi) 

      Refer to Circuit/System Testing - Fuel Pressure Drops Off.

    • If less than 45 kPa (6.5 psi)/60 kPa (8.7 psi) 
  9. If the fuel system components test normal, refer to Symptoms - Engine Controls , and Fuel Injector Diagnosis  for further diagnosis.
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