how to fix P0420 code on my Toyota Corolla E210 (2019-2024)

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative terminal of the battery to prevent electrical issues.
• Allow the engine to cool down before starting work.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, torque wrench, penetrating oil.
• If oxygen sensor tests indicate malfunction:
  • Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
  • Apply penetrating oil to the O2 sensor threads and wait a few minutes.
  • Using the O2 sensor socket, carefully remove the faulty sensor(s).
  • Install the new oxygen sensor, torque to manufacturer specifications (typically around 30 ft-lbs).

3. Check and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, torque wrench, exhaust pipe cutter, gasket scraper, new exhaust gaskets, and clamps.
• If the catalytic converter is confirmed faulty:
  • Disconnect the exhaust from the manifold and the rear exhaust section.
  • Remove the catalytic converter by unbolting it from its mounts.
  • Clean any old gasket material from the mounting surfaces.
  • Install the new catalytic converter, ensuring it is positioned correctly, and torque the bolts to manufacturer specifications.
  • Reconnect the exhaust system and check for leaks.

4. Reset the Engine Control Module (ECM)

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the P0420 code and any other related error codes.