Circuit/System Verification

Observe the DTC information with a scan tool. DTC P2177, P2179, P2187, or P2189 should not set.
- If any other DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle to diagnosis the applicable DTC.
Ignition ON, observe the barometric pressure (BARO) sensor pressure parameter and compare the reading on the scan tool to the barometric pressure table. Refer to Altitude Versus Barometric Pressure .
- If the BARO sensor pressure is not within the range specified for your altitude, refer to DTC P2227, P2228, or P2229 .
Engine at normal operating temperature, observe the Total Fuel Trim Avg. parameter with a scan tool. The Total Fuel Trim Avg. should be between -22 to +23 percent.
- If not within the specified range, inspect for the following conditions:
  - A mass air flow (MAF) sensor signal that is skewed-If the Short Term FT parameters for both banks changes greater than 20 percent when the MAF sensor is disconnected, refer to DTC P0101 .
  - The air intake system after the MAF sensor for vacuum leaks
  - Fuel contamination-Refer to Alcohol/Contaminants-in-Fuel Diagnosis and Fuel System Cleaning .
  - Splits, kinks, or improper connections at the vacuum hoses-Refer to Emission Hose Routing Diagram .
  - The fuel system is operating lean. Refer to Fuel System Diagnosis .
  - Vacuum leaks at the intake manifold or throttle body
  - Leaking crankcase ventilation system
  - The engine control module grounds for being clean, tight, and in the correct locations
  - A high engine oil level condition-A high engine oil level causes oil residue to form on the mass air flow (MAF) sensor, causing a lean indication. The MAF sensor does not need to be replaced.
  - Vacuum leaks that only affect one bank of the engine-For example, the intake manifold, the injector O-rings.
  - Lean injectors-Refer to Fuel Injector Solenoid Coil Test .
  - Missing, restricted, or leaking exhaust components-Refer to Symptoms - Engine Exhaust .
  - The heated oxygen sensor (HO2S) is installed securely and the electrical connector is not contacting the exhaust system.
  - An engine mechanical condition-Refer to Symptoms - Engine Mechanical .
Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.