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Home >> Chevrolet >> 2015 >> Cruze LT, Automatic Trans >> Repair and Diagnosis >> External Pages >> Different car >> Section 89 (Engine Controls And Fuel - 1.4L (LUJ LUV) - DTC P0010 To DTC P0246) >> Diagnostic Information and Procedures >> DTC P0171 or P0172: Fuel Trim System >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2015 Chevrolet Trax and 2015 Buick Encore. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition ON.
  2. Verify the manifold absolute pressure sensor is within the range specified for your altitude. Refer to Altitude Versus Barometric Pressure
    • If not within the specified range 

      Refer to DTC P0106 

    • If within the specified range 
  3. Engine running at the operating temperature.
  4. Verify the Long Term Fuel Trim parameter is between -30 % and +35 %.
    • If greater than +35 % 
    1. Ignition OFF.
    2. Inspect for the conditions listed below:
      • Mass air flow (MAF) sensor signal skewed. If the Short Term Fuel Trim parameter changes greater than 20 % when the MAF sensor is disconnected, refer to DTC P0101 .
      • 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 .
      • Split, kinked, or improperly connected vacuum hoses
      • Insufficient fuel in the tank
      • Low fuel pressure. Refer to Fuel System Diagnosis (LUJ)Fuel System Diagnosis (LUV) .
      • 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
      • Leaks in the crankcase ventilation system.
        • If a condition is found, repair as necessary.
        • If no condition is found, test the engine for a mechanical condition. Refer to Symptoms - Engine Mechanical .
    • If less than -30 % 
    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 .
      • 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 (LUJ)Fuel System Diagnosis (LUV)
      • 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, test the engine for a mechanical condition. Refer to Symptoms - Engine Mechanical .
    • If between -30 % and +35 % 
  5. All OK.
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