Inspection Procedure

HINT: 

• If a malfunction cannot be found when troubleshooting DTC P0420, a lean or rich abnormality may be cause. Perform troubleshooting by following the inspection procedure for P0171 (System Too Lean) and P0172 (System Too Rich).
• Sensor 1 refers to the sensor closest to the engine assembly.
• Sensor 2 refers to the sensor farthest away from the engine assembly.
• Read freeze frame data using the Techstream. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air fuel ratio was lean or rich, and other data from the time the malfunction occurred.