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

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 negative battery terminal to prevent electrical short circuits.

2. Oxygen Sensor Replacement (if needed)

• Tools Required: O2 sensor socket, ratchet and extension, torque wrench.
• Sub-steps:
  1. Locate the upstream oxygen sensor (before the catalytic converter).
  2. Disconnect the electrical connector from the oxygen sensor.
  3. Use the O2 sensor socket to remove the sensor from the exhaust manifold.
  4. Install the new oxygen sensor by screwing it in hand-tight, then torque to the manufacturer’s specification (typically around 30-40 lb-ft).
  5. Reconnect the electrical connector.

3. Catalytic Converter Inspection/Replacement

• Tools Required: Socket set, torque wrench, exhaust pipe cutter (if necessary), gasket scraper.
• Sub-steps:
  1. Inspect the catalytic converter for damage or blockage. If it is damaged, proceed to replace it.
  2. If replacing, remove the exhaust pipes connected to the catalytic converter using a socket set.
  3. If necessary, use an exhaust pipe cutter to remove bolts that are rusted or difficult to access.
  4. Clean the mating surfaces of the exhaust pipe and the new catalytic converter.
  5. Install the new catalytic converter and secure it with new gaskets and bolts. Torque the bolts to the manufacturer's specifications (usually around 30 lb-ft).
  6. Reinstall the exhaust pipes.

4. Final Checks

• Reconnect the negative battery terminal.
• Start the engine and allow it to reach operating temperature while checking for exhaust leaks.