how to diagnose P0420 code on my Toyota Corolla E140 (2006-2013)

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the engine to cool down before working on the exhaust system.

2. Inspect and Replace Oxygen Sensors

1. Locate the Oxygen Sensors:
   • The upstream sensor is usually located before the catalytic converter, and the downstream sensor is located after it.
2. Disconnect the Sensors:
   • Unplug the electrical connectors from both oxygen sensors.
3. Remove the Sensors:
   • Use an oxygen sensor socket or wrench to carefully remove the sensors from their respective exhaust pipe locations.
4. Install New Sensors:
   • Apply anti-seize compound (if not pre-applied) to the threads of the new sensors.
   • Install the new sensors and tighten them to manufacturer specifications (typically around 30 lb-ft).
5. Reconnect the Sensors:
   • Plug in the electrical connectors to the new sensors.

3. Inspect and Replace the Catalytic Converter (if necessary)

1. Exhaust System Inspection:
   • If the oxygen sensors are functioning correctly, inspect the catalytic converter for any damage or clogging.
2. Remove the Catalytic Converter:
   • Use a socket set to remove the bolts securing the catalytic converter to the exhaust system.
   • Carefully detach the catalytic converter from the exhaust system and remove it.
3. Install New Catalytic Converter:
   • Position the new catalytic converter in place and secure it with bolts.
   • Torque the bolts to manufacturer specifications (typically around 30 lb-ft).
4. Reconnect Exhaust System:
   • Ensure all connections are tight and seal any joints as necessary.