Circuit/System Verification

WARNING: This page is about a different car, the 2010 GMC Sierra and 2010 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.

Ignition OFF, open the hood to disable the Auto-Stop function. Refer to Hybrid Modes of Operation Description .
Ignition ON, verify the scan tool hood position parameter displays Open.
- If the hood position does not display Open, refer to Diagnostic Trouble Code (DTC) List - Vehicle for DTC P254F.
Engine running, observe the DTC information with a scan tool. Verify there are no HO2S DTCs set.
- If any DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .
Ignition ON, 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 pressure is not within the range specified for your altitude, refer to DTC P0106 .
With the engine idling, observe the Mass Air Flow (MAF) Sensor parameter. The MAF Sensor parameter should be within 2-6 g/s at idle.
- If not within the specified range, refer to DTC P0101 or P1101 (Without Heavy Duty L96) or DTC P0102 or P0103 (Without Heavy Duty L96) .

NOTE: EVAP purge enablement may cause the FT to be momentarily outside the normal range.

Engine at normal operating temperature, observe the scan tool Long Term FT parameter. The reading should be between -19 to +19 percent.
- If not within the specified range, verify none of the following conditions exist:
  P0171 or P0174
  - Vacuum hoses for splits, kinks, and improper connections
  - Insufficient fuel in the tank
  - Low fuel pressure-Refer to Fuel System Diagnosis (Without FPCM) or Fuel System Diagnosis (FPCM) .
  - Fuel contamination-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (Special Tool) .
  - Malfunctioning fuel injectors-Refer to Fuel Injector Diagnosis (CH 47976) or Fuel Injector Diagnosis (J 39021 or Tech 2) .
  - Missing, restricted, or leaking exhaust components-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 filter element
  - A cracked EVAP canister
  - Evaporative pipes obstructed or leaking
  - The crankcase ventilation system for leaks
  P0172 or P0175
  - The air intake duct for being collapsed or restricted
  - The air filter for being dirty or restricted
  - Objects blocking the throttle body
  - Excessive fuel in the crankcase
  - The evaporative emissions control system for improper operation
  - Missing, restricted, or leaking exhaust components-Refer to Fuel System Diagnosis (Without FPCM) or Fuel System Diagnosis (FPCM) .
  - Malfunctioning fuel injectors-Refer to Fuel Injector Diagnosis (CH 47976) or Fuel Injector Diagnosis (J 39021 or Tech 2) .
  - Fuel contamination-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (Special Tool) .
If all conditions test normal, test the engine for a 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.