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

Solution

1. Preparation

• Gather all necessary tools and replacement parts.
• Disconnect the negative battery terminal to ensure safety.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, torque wrench, penetrating oil.
• Sub-steps:
  1. Locate the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
  2. Spray penetrating oil on the sensor threads to aid removal.
  3. Use the O2 sensor socket to remove the upstream oxygen sensor. Disconnect the electrical connector.
  4. Repeat the above steps for the downstream oxygen sensor.
  5. Install the new oxygen sensors by reversing the removal steps, ensuring they are torqued to the manufacturer's specifications (usually around 30 lb-ft).

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, torque wrench, exhaust gasket (if applicable), safety goggles, gloves.
• Sub-steps:
  1. Raise the vehicle securely using jack stands.
  2. Remove the exhaust pipes connected to the catalytic converter using the socket set, noting the arrangement for reassembly.
  3. Inspect the catalytic converter for any visible damage or clogging.
  4. If replacement is needed, remove the old catalytic converter and install the new one, ensuring that the exhaust gaskets are replaced if necessary.
  5. Reattach the exhaust pipes and tighten the bolts to the manufacturer's specifications.

4. Clear Codes and Test

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