P0171 or P0174

Allow the engine to reach operating temperature. With the engine running, observe the affected Long Term FT parameter with a scan tool. The reading should be between 0-23 percent.

• If not within the specified range, inspect for the following:

• With the ignition ON and the engine OFF, observe the manifold absolute pressure (MAP) sensor parameter. The MAP sensor pressure should be within the range specified for your altitude. Refer to Altitude Versus Barometric Pressure .
  • If the MAP sensor does not indicate the correct barometric pressure, refer to DTC P0106  and DTC P0107 or P0108 .
• Vacuum hoses for splits, kinks, and improper connections
• Insufficient fuel in the tank
• A malfunctioning MAF-Refer to DTC P0068 or P0121  or DTC P0101 or P1101 .
• Low fuel pressure-Refer to Fuel System Diagnosis .
• Fuel contamination-Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
• Malfunctioning fuel injectors-Refer to Fuel Injector Diagnosis (CH47976) or Fuel Injector Diagnosis (J39021 or Tech 2) .
• Missing, loose, or leaking exhaust components from the HO2S forward-Refer to Symptoms - Engine Exhaust .
• Vacuum leaks at the intake manifold, the throttle body, and the injector O-rings
• The air induction system and the air intake ducts for leaks or for a missing air filter element
• A cracked or damaged EVAP canister
• Evaporative canister purge lines plugged or obstructed
• The crankcase ventilation system for leaks-Refer to Crankcase Ventilation System Inspection/Diagnosis .
• The HO2S for improper installation and for electrical wires or connectors that may have contacted the exhaust system
• The HO2S signal circuit open, shorted to ground, or shorted to the low reference circuit
• The HO2S sensor 1 low signal circuit for an open circuit or high resistance
• Malfunctioning engine components-Refer to Symptoms - Engine Mechanical .