why is my Toyota Corolla E140 (2006-2013) check engine light on with code P0420

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the battery to prevent electrical shorts.

2. Oxygen Sensor Replacement

• Tools Required: O2 sensor socket, ratchet, torque wrench.
• Remove the faulty oxygen sensor located before or after the catalytic converter.
  • Disconnect the electrical connector.
  • Use the O2 sensor socket to unscrew the sensor.
• Install the new oxygen sensor.
  • Apply anti-seize compound to the threads (if necessary).
  • Torque the sensor to the manufacturer's specifications (typically around 30 ft-lbs).
  • Reconnect the electrical connector.

3. Catalytic Converter Inspection and Replacement

• Tools Required: Socket set, torque wrench, exhaust pipe cutter (if necessary).
• Inspect the catalytic converter for signs of clogging (e.g., rattling noise when shaken).
• If damaged, remove the catalytic converter.
  • Use an exhaust pipe cutter or saw to cut the exhaust pipes if necessary.
  • Unbolt any mounting brackets and remove the converter.
• Install the new catalytic converter.
  • Position the new converter and secure it with bolts.
  • Ensure all connections are tight and free of leaks.
  • Torque to specifications as per the service manual.

4. Clear Codes and Test Drive

• Reconnect the battery.
• Use the OBD-II scanner to clear the P0420 code.
• Start the engine and perform a test drive to monitor for any reoccurrence of the check engine light.