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Home >> Chevrolet >> 2018 >> Suburban 3500 HD LT >> Repair and Diagnosis >> External Pages >> Different car >> Section 2 (Engine Controls And Fuel - 5.3L (L83) Or 6.2L (L86) - DTC P0010 To DTC P0442) >> Diagnostic Information And Procedures >> DTC P0171, P0172, P0174 Or P0175: Fuel Trim System >> Circuit/System Testing

Circuit/System Testing

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  1. Ignition ON.
  2. Verify the MAP sensor pressure parameter is within the range specified for your altitude. Refer to Altitude Versus Barometric Pressure .
    • If not within the specified range 

      Refer to DTC P0106 .

    • Go to next step : If within the specified range 
  3. Engine running at the operating temperature.
  4. Verify the Long Term Fuel Trim Bank 1 or 2 parameter is between -10% and +10%.
    • If greater than +10% : 
    1. Ignition OFF.
    2. Inspect for the conditions listed below :
      • Mass air flow sensor signal skewed - If the Short Term Fuel Trim parameters for both banks changes greater than 20 % when the MAF sensor is disconnected, refer to DTC P0101 .
      • Contamination of the mass air flow sensor with oil or other foreign material.
      • Fuel contamination - Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
      • Missing, restricted, or leaking exhaust components - Refer to Symptoms - Engine Exhaust .
      • Malfunctioning fuel injectors - Refer to Fuel Injector Diagnosis .
      • Vacuum hoses for splits, kinks and improper connections.
      • Insufficient fuel in the tank.
      • Partial blockage of the air filter element or other conditions that alter air flow to the mass air flow sensor.
      • Low fuel pressure - Refer to Fuel System Diagnosis .
      • Vacuum leaks at the intake manifold, the throttle body and the injector O-rings.
      • Leaks in the air induction system and the air intake ducts.
      • Missing air filter element.
      • Cracked EVAP canister.
      • Evaporative pipes obstructed or leaking.
      • The crankcase ventilation system for leaks - Refer to Crankcase Ventilation System Inspection/Diagnosis .
        • If a condition is found, repair as necessary.
        • If no condition is found, inspect the engine for a mechanical condition. Refer to Symptoms - Engine Mechanical .
    • If less than -10% 
    1. Ignition OFF.
    2. Inspect for the conditions listed below :
      • Mass air flow (MAF) sensor signal skewed - If the Short Term Fuel Trim parameters for both banks changes greater than 20 % when the MAF sensor is disconnected, refer to DTC P0101 .
      • Contamination of the mass air flow sensor with oil or other foreign material.
      • Fuel contamination - Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
      • Missing, restricted, or leaking exhaust components - Refer to Symptoms - Engine Exhaust .
      • Malfunctioning fuel injectors - Refer to Fuel Injector Diagnosis .
      • Collapsed or restricted air intake duct.
      • Excessive fuel pressure - Refer to Fuel System Diagnosis .
      • Dirty or restricted air filter.
      • Objects blocking the throttle body.
      • Improper operation of the evaporative emissions control system.
      • Excessive fuel in the crankcase - Change the engine oil as necessary.
        • If a condition is found, repair as necessary.
        • If no condition is found, inspect the engine for a mechanical condition. Refer to Symptoms - Engine Mechanical .
    • Go to next step : If between -10% and +10% 
  5. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed in the Freeze Frame/Failure Records data.
  6. Verify DTC P0171, P0172, P0174 or P0175 is not set.
    • If any of the DTCs set 

      Refer to conditions listed above.

    • Go to next step : If none of the DTCs set 
  7. All OK.
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