• 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:Catalytic Converter Description and Operation

• DTCs related to the following system/component = Not Set
• B17 Barometric Pressure Sensor
• B23 Camshaft Position Sensor
• B34 Engine Coolant Temperature Sensor
• B52 Heated Oxygen Sensor
• B66 Intake Air Temperature Sensor
• B74 Manifold Absolute Pressure Sensor
• B75C Multifunction Intake Air Sensor
• B150 Fuel Tank Pressure Sensor
• B198 Fuel Composition Sensor
• Q12 Evaporative Emission Purge Solenoid Valve
• Q17 Fuel Injector
• Q38 Throttle Body
• Engine Misfire
• Evaporative Emission (EVAP) System
• Fuel Trim System
• Secondary Air Injection System
• BARO Sensor=Greater than 70 kPa (10.2 PSI)
• Engine Coolant Temperature@Cold Start-Up=Warmer than −20°C (−4°F)
• Evaporative Emission (EVAP) Purge System=Inactive
• IAT Sensor=−20 to 200°C (−4 to 392°F)
• MAP Sensor=10 to 255 kPa (1.5 to 37 PSI)

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

Fuel Trim System=Not within a calibrated range

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.

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Control Module References

1. Ignition » On / Vehicle » In Service Mode
2. Verify DTC P0420 is not set
• If the DTC is set

  Refer to:DTC P0420

• If the DTC is not set
3. Verify there are no DTCs set related to the following component/system:
• B17 Barometric Pressure Sensor
• B23 Camshaft Position Sensor
• B34 Engine Coolant Temperature Sensor
• B52 Heated Oxygen Sensor
• B66 Intake Air Temperature Sensor
• B74 Manifold Absolute Pressure Sensor
• B75C Multifunction Intake Air Sensor
• B150 Fuel Tank Pressure Sensor
• B198 Fuel Composition Sensor
• Q12 Evaporative Emission Purge Solenoid Valve
• Q17 Fuel Injector
• Q38 Throttle Body
• Engine Misfire
• Evaporative Emission (EVAP) System
• Fuel Trim System
• Secondary Air Injection System
• If a related DTC is set

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

• If a related DTC is not set
4. Verify the following conditions do not exist:
• Air Cleaner Element—Dirty/Missing/Restricted/Visible Damage/Water intrusion
• Engine—Vacuum leak
• Evaporative Emission (EVAP) Purge System—Leaking/Stuck Open
• Evaporative Emission (EVAP) System—Leaking/Saturated with fuel/Visible Damage
• Exhaust System—Leaking/Restricted»Refer to:Symptoms - Engine Exhaust
• Fuel—Contaminated/Poor Quality»Refer to:Alcohol/Contaminants-in-Fuel Diagnosis
• Fuel Injectors—Restricted/Leaking»Refer to:Fuel Injector Diagnosis
• Fuel pressure that is too low or too high.»Refer to:Fuel System Diagnosis
• Intake Air Duct—Loose/Poor Connection/Visible Damage/Leaking/Restricted
• Insufficient amount of fuel in the tank.
• Positive Crankcase Ventilation System—Dirty/Poor Connection/Restricted/Leaking
• Throttle Body—Blocked/Dirty/Restricted
• Vacuum Hoses—Incorrect connection/Kinked/Leaking/Restricted
• If a condition exists

  Repair or replace as necessary

• If no condition exists
5. All OK.

Perform the Diagnostic Repair Verification after completing the repair:Diagnostic Repair Verification