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Home >> Chevrolet >> 2020 >> Express 2500 LS, 6.0L Eng VIN G >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 24 (Engine Controls And Fuel - 2.8L (LWN) Diesel - Diagnostic Information And Procedures (1 Of 3)) >> Diagnostic Information and Procedures >> DTC P0191-P0194, P127C, or P127D >> Circuit/System Verification

Circuit/System Verification

WARNING: This page is about a different variant/trim than selected.
  1. Ignition - On / Vehicle - In Service Mode
  2. Verify the scan tool parameter : Fuel Rail Pressure Sensor 1 & Fuel Rail Pressure Sensor 2 = 0.4 to 4.5 V and changes
    • If not between 0.4 and 4.5 V or does not change 

      Refer to : Circuit/System Testing

    • Go to next step : If between 0.4 and 4.5 V and changes 
  3. Engine Running
  4. Perform the scan tool control function : Fuel Rail Pressure - Increase & Decrease

    Verify the scan tool parameter : Fuel Rail Pressure Sensor = The value should change with each command.

    • If the value does not change 

      Refer to : Circuit/System Testing

    • Go to next step : If the value changes 
  5. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

    Verify the DTC does not set.

    • If the DTC sets 

      Refer to : Circuit/System Testing

    • Go to next step : If the DTC is not set 
  6. All OK.