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

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the negative terminal of the battery to ensure safety while working.
• Allow the exhaust system to cool before starting work.

2. Inspect and Replace Oxygen Sensors

• Sub-steps:
  1. Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors. These are typically found on the exhaust manifold and after the catalytic converter, respectively.
  2. Unplug the electrical connectors from both oxygen sensors.
  3. Use an oxygen sensor socket to remove the sensors from the exhaust system.
  4. Apply anti-seize compound to the threads of the new sensors to facilitate easier removal in the future.
  5. Install the new sensors, ensuring they are tightened to the manufacturer’s torque specifications (typically around 30 ft-lbs).
  6. Reconnect the electrical connectors to the new sensors.

3. Inspect and Replace Catalytic Converter (if necessary)

• Sub-steps:
  1. If the diagnostic steps indicate a failing catalytic converter, prepare to remove it.
  2. Support the vehicle securely on jack stands and remove any heat shields if present.
  3. Use a socket set to unbolt the catalytic converter from the exhaust system. There may be bolts connecting it to the exhaust manifold and the mid-pipe.
  4. Inspect the mounting gaskets and replace them if they are degraded or damaged.
  5. Install the new catalytic converter, ensuring it is positioned correctly and all bolts are tightened to the specified torque (around 30 ft-lbs).
  6. Reinstall any heat shields that were removed.

4. Clear Codes and Test

• Sub-steps:
  1. Reconnect the negative battery terminal.
  2. Use the OBD-II scanner to clear the P0420 code from the vehicle's computer.
  3. Start the engine and allow it to reach operating temperature.
  4. Take the vehicle for a test drive to ensure the check engine light does not reappear.