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Home >> Chevrolet >> 2020 >> Express 2500 LS, 6.0L Eng VIN G >> Repair and Diagnosis >> External Pages >> Different car >> Section 113 (Engine Controls And Fuel - 4.3L (LV1) - Diagnostic Information And Procedures (2 Of 2)) >> Diagnostic Information and Procedures >> Fuel System Diagnosis >> Circuit/System Verification

Circuit/System Verification

WARNING: This page is about a different car, the 2019 GMC Savana 3500, 2019 GMC Savana 2500, 2019 Chevrolet Express 3500, and 2019 Chevrolet Express 2500. However, it is still accessible from the selected car via links, so may be relevant.
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 %.
  1. Ignition ON, engine OFF, command the Fuel Pump Enable On several times with a scan tool.
  2. Verify the scan tool Fuel Pressure Sensor parameter is between 320 - 580 kPa (46 - 84 PSI).
    • If less than 320 kPa (46 PSI) 

      Refer to Circuit/System Testing - Fuel Pressure Low.

    • If greater than 580 kPa (84 PSI) 

      Replace the G12 Fuel Pump.

    • Go to next step: If between 320 - 580 kPa (46 - 84 PSI) 
    3. 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.

  3. Verify that the scan tool Fuel Pressure Sensor parameter, after the fuel pump is turned off, decreases to less than 544 kPa (79 PSI).
    • If greater than 544 kPa (79 PSI) 

      Replace the G12 Fuel Pump.

    • Go to next step: If less than 544 kPa (79 PSI) 
  4. Verify that the scan tool Fuel Pressure Sensor parameter does not decrease greater than 34 kPa (5 PSI) in 1 min.
    • If greater than 34 kPa (5 PSI) 

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

    • Go to next step: If less than 34 kPa (5 PSI) 
  5. Relieve the fuel pressure to 69 kPa (10 PSI), refer to Fuel Pressure Relief .
  6. Verify that the fuel pressure does not decrease greater than 14 kPa (2 PSI) in 5 minutes.
    • If the fuel pressure decreases greater than 14 kPa (2 PSI) 

      Replace the G12 Fuel Pump.

    • Go to next step: If the fuel pressure does not decrease greater than 14 kPa (2 PSI) 
  7. Verify that the scan tool Fuel 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.

    • Go to next step: If less than 45 kPa (6. 5 PSI) / 60 kPa (8. 7 PSI) 
  8. If the fuel system components test normal, refer to Symptoms - Engine Controls , and Fuel Injector Diagnosis  for further diagnosis.
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