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Home >> Chevrolet >> 2013 >> Sonic RS, Standard Trans >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 11 (Engine Controls/Fuel - 1.8L (LUW, LWE) - DTC P0010 To DTC P0442) >> Diagnostic Information and Procedures >> DTC P0171 or P0172 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different variant/trim than selected.
  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, allow the engine to reach operating temperature.
  4. Verify the Long Term Fuel Trim parameter is between -25 % and +25 % (LWE) or -30 % and +30 % (LUW).
    • If not within the specified range, verify that none of the conditions listed below exist: 

    P0171

    • 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 .
    • 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. Refer to Crankcase Ventilation System Inspection/Diagnosis .

    P0172

    • 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
    • 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 
  5. Test the engine for a mechanical condition. Refer to Symptoms - Engine Mechanical .
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