• Perform the Diagnostic System Check prior to using this diagnostic procedure:Diagnostic System Check - Vehicle
• Review the description of Strategy Based Diagnosis:Strategy Based Diagnosis
• An overview of each diagnostic category can be found here:Diagnostic Procedure Instructions

For an overview of the component/system, refer to:Fuel System Description

• DTCs related to the following system/component = Not Set
• B52 Heated Oxygen Sensor
• B65 Intake Manifold Pressure and Air Temperature Sensor
• B74 Manifold Absolute Pressure Sensor
• B75C Multifunction Intake Air Sensor
• B198 Fuel Composition Sensor
• Q12 Evaporative Emission Purge Solenoid Valve
• Q17 Fuel Injector
• Q38 Throttle Body
• Engine Misfire
• Barometric Pressure=Greater than 70 kPa (10 PSI)
• Engine Coolant Temperature=−20 to 150°C (−7 to 302°F)
• Engine Speed=400 to 6,100 RPM
• Fuel Control Loop Status=Closed Loop
• Fuel level=Greater than 10%
• IAT Sensor=−20 to 150°C (−7 to 302°F)
• MAF Sensor=1 to 510 g/s
• Manifold Absolute Pressure=5 to 255 kPa (.725 to 37 PSI)

Frequency the DTC runs=Continuously—After the running conditions are met

The limit to correct a lean air/fuel ratio has been exceeded.—After the running conditions are met—For greater than 3 min

The limit to correct a rich air/fuel ratio has been exceeded.—After the running conditions are met—For greater than 3 min

DTCs listed in the DTC Descriptor category=Type B DTC

DTCs listed in the DTC Descriptor category=Type B DTC

• Inspect for aftermarket devices which may affect the operation of the system.
• The ideal fuel trim values are around 0%. A positive fuel trim value indicates that the ECM is adding fuel in order to compensate for a lean condition. A negative fuel trim value indicates that the ECM is reducing the amount of fuel in order to compensate for a rich condition.

Engine Controls Schematics

Master Electrical Component List

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Control Module References

1. Ignition » On / Vehicle » In Service Mode
2. Verify there are no DTCs set related to the following component/system:
• B52 Heated Oxygen Sensor
• B65 Intake Manifold Pressure and Air Temperature Sensor
• B74 Manifold Absolute Pressure Sensor
• B75C Multifunction Intake Air Sensor
• B198 Fuel Composition Sensor
• Q12 Evaporative Emission Purge Solenoid Valve
• Q17 Fuel Injector
• Q38 Throttle Body
• Engine Misfire
• If a related DTC is set

  Refer to:Diagnostic Trouble Code (DTC) List - Vehicle

• If a related DTC is not set
3. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

   Verify DTC P0171, P0172 is not set

• If the DTC sets

  Refer to: Circuit/System Testing

• If no DTC is set
4. All OK.

1. Ignition » On / Vehicle » In Service Mode
2. Verify the scan tool parameter:MAP Sensor=Altitude Versus Barometric Pressure—The value should be within the range listed in the table.
• If not in the specified range

  Refer to:DTC P0106, P0107, or P0108

• If in the specified range
3. Engine » Idling — At normal operating temperature
4. Observe the scan tool parameter:Short Term Fuel Trim

   Disconnect the component:B75 Mass Air Flow Sensor

   Verify the scan tool parameter:Short Term Fuel Trim=Change is less than 20%

• If the change is 20% or greater

  Refer to:DTC P0101

• If the change is less than 20%
5. Connect the component:B75 Mass Air Flow Sensor
6. Verify the scan tool parameter:Long Term Fuel Trim=−10 to 10%
• If greater than 10%
1. Ignition/Vehicle » Off
2. Verify the following conditions do not exist:
• Air Cleaner Element—Missing
• Evaporative Emission Canister—Cracked
• Evaporative Emission Pipe—Leaking/Restricted
• Exhaust System—Cracked/Leaking/Loose Clamps/Missing components/Restricted/Visible Damage»Refer to:Symptoms - Engine Exhaust
• Fuel—Contaminated/Poor Quality»Refer to:Alcohol/Contaminants-in-Fuel Diagnosis
• Fuel level—Low
• Fuel Injectors—Malfunction/Restricted»Refer to:Fuel Injector Diagnosis
• Fuel Pressure—Low»Refer to:Fuel System Diagnosis
• Induction System/Intake Air Duct—Leaking
• Intake Manifold/O-Ring—Fuel Injector/Throttle Body—Leaking
• MAF Sensor—Contamination of the measuring element/Water intrusion
• Positive Crankcase Ventilation System—Leaking/Restricted»Refer to:Crankcase Ventilation System Inspection/Diagnosis
• Vacuum Hoses—Cracked/Leaking/Kinked/Loose Clamps/Missing components/Restricted
• If a condition exists » Repair or replace as necessary
• If no condition exists»Refer to:Symptoms - Engine Mechanical
• If less than −10%
1. Ignition/Vehicle » Off
2. Verify the following conditions do not exist:
• Air Cleaner Element—Restrictions
• Catalyst System—Restrictions»Refer to:Symptoms - Engine Exhaust
• Engine Oil—Contaminated/Fuel»Change the engine oil and filter.
• Evaporative Emission (EVAP) System—Malfunction
• Exhaust System—Cracked//Leaking/Loose Clamps/Missing components/Restricted/Visible Damage»Refer to:Symptoms - Engine Exhaust
• Fuel—Contaminated/Poor Quality»Refer to:Alcohol/Contaminants-in-Fuel Diagnosis
• Fuel Injectors—Malfunction»Refer to:Fuel Injector Diagnosis
• Fuel Pressure—High»Refer to:Fuel System Diagnosis
• Intake Air Duct—Collapsed/Restricted
• MAF Sensor—Contamination of the measuring element/Water intrusion
• Oil consumption»Refer to:Oil Consumption Diagnosis
• Positive Crankcase Ventilation System—Leaking/Restricted»Refer to:Crankcase Ventilation System Inspection/Diagnosis
• Throttle Body—Blocked/Carbon Tracking»Refer to:Throttle Body Cleaning
• If a condition exists » Repair or replace as necessary
• If no condition exists»Refer to:Symptoms - Engine Mechanical
• If between -10 and 10%
7. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

   Verify DTC P0171, P0172 is not set

• If the DTC sets

  Repeat step 4

• If no DTC is set
8. All OK.

• For control module replacement, programming, and setup refer to:Control Module References
• Perform the special tool function:Fuel Trim Reset