my Toyota Corolla E210 (2019-2024) has a P0420 code and is failing emissions, how to fix?

Solution

1. Preparation

• Gather tools and parts required.
• Disconnect the vehicle's battery to ensure safety during repairs.
• Raise the vehicle on jack stands and ensure it is secure.

2. Inspect and Replace Oxygen Sensors

1. Remove the Oxygen Sensors:
   • Locate the pre-catalytic and post-catalytic oxygen sensors.
   • Use an oxygen sensor socket to remove both sensors from the exhaust system.
2. Install New Oxygen Sensors:
   • Apply anti-seize compound on the threads of the new sensors to prevent them from seizing.
   • Install the new sensors, tightening them to the manufacturer’s specified torque (usually around 30 lb-ft).
   • Reconnect the electrical connectors.

3. Check and Replace Catalytic Converter (if necessary)

1. Inspect Catalytic Converter:
   • If the temperature test indicated a significant difference (more than 100°F), proceed to replace the catalytic converter.
2. Remove the Old Catalytic Converter:
   • Unbolt the catalytic converter from the exhaust system using a socket set.
   • Disconnect any heat shields or brackets if necessary.
3. Install the New Catalytic Converter:
   • Align the new catalytic converter in place and secure it using the appropriate hardware, tightening to the specified torque.
   • Reinstall any heat shields or brackets removed earlier.

4. Reset the Check Engine Light

• Reconnect the battery and use the OBD-II scanner to clear the P0420 code.

5. Test Drive

• Start the vehicle and allow it to reach operating temperature.
• Perform a test drive to ensure the check engine light does not reappear and monitor for any abnormal symptoms.