Circuit/System Testing: P0172

Allow the engine to reach operating temperature. With the engine running, observe the affected Long Term FT parameter with a scan tool. The value should be more than approximately -25 percent with the engine running at operating temperature.

• If the value is not more than -25 percent, 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  .
• With the engine idling and the transmission in the Park or Neutral position, observe the manifold absolute pressure (MAP) sensor parameter. The MAP sensor parameter should be between 19-42 kPa.
  • If the MAP sensor parameter is not between 19-42 kPa, refer to DTC P0106  .
• With the engine idling, observe the mass air flow (MAF) sensor parameter. The MAF sensor parameter should be between 3-10 g/s at idle.
  • If the MAF sensor parameter is not between 3-10 g/s at idle, refer to DTC P0101  or DTC P0102 or P0103  .
• Vacuum hoses for splits, kinks, and improper connections
• The air duct for being collapsed or restricted
• The air filter for being dirty or restricted
• Objects blocking the throttle body
• Excessive fuel in the crankcase due to leaking fuel injectors-Refer to Fuel Injector Diagnosis (w/J39021 or Tech 2) or Fuel Injector Diagnosis (w/CH47976) .
• The evaporative emissions control system for improper operation
• Excessive fuel pressure-Refer to Fuel System Diagnosis .
• Malfunctioning fuel injectors-Refer to Fuel Injector Diagnosis (w/J39021 or Tech 2) or Fuel Injector Diagnosis (w/CH47976) .
• Fuel contamination-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (With Special Tool) .
• The HO2S 1 for improper installation and for electrical wires or connectors that may have contacted the exhaust system
• The HO2S 1 signal circuit shorted to voltage
• Malfunctioning engine components-Refer to Symptoms - Engine Mechanical .

Repair or replace as necessary.