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

Solution

1. Preparation

• Gather necessary tools and parts.
• Park the vehicle on a level surface and engage the parking brake.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Replace Oxygen Sensors (if faulty)

• Tools Required: O2 sensor socket, ratchet, torque wrench.
• Instructions:
  1. Locate the upstream and downstream oxygen sensors; the upstream sensor is typically before the catalytic converter, while the downstream is after.
  2. Disconnect the electrical connectors from both O2 sensors.
  3. Use an O2 sensor socket to remove the upstream sensor first.
  4. Install the new upstream O2 sensor by threading it into the exhaust pipe, then tighten it to the manufacturer’s torque specification (typically around 30-40 lb-ft).
  5. Repeat the process for the downstream O2 sensor.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, wrench set, exhaust hanger removal tool.
• Instructions:
  1. Inspect the catalytic converter for any visible damage or signs of overheating (discoloration).
  2. If replacement is necessary, remove the exhaust hangers using the exhaust hanger removal tool.
  3. Disconnect the exhaust pipes at both ends of the catalytic converter by removing the bolts or clamps.
  4. Remove the old catalytic converter and replace it with a new unit, ensuring proper alignment.
  5. Reattach the exhaust pipes and tighten all bolts to the recommended torque specification.

4. Reset the ECU

• Instructions:
  1. Reconnect the negative battery terminal.
  2. Use the OBD-II scanner to clear the P0420 code from the ECU.
  3. Start the vehicle and allow it to reach operating temperature.