how to fix P0420 code on Toyota Highlander XU70 (2020-Present)

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical short circuits.
• Allow the engine to cool down completely before starting work.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, and torque wrench.
• Sub-steps:
  1. Locate the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
  2. Disconnect the electrical connectors from both sensors.
  3. Remove the upstream and downstream sensors using the O2 sensor socket.
  4. Install new sensors and torque them to the manufacturer specification (typically around 30 ft-lbs).
  5. Reconnect the electrical connectors.

3. Inspect and Replace the Catalytic Converter

• Tools Required: Socket set, torque wrench, sawzall (if necessary), and exhaust clamps.
• Sub-steps:
  1. Inspect the catalytic converter for physical damage or clogging.
  2. Remove any heat shields or brackets securing the catalytic converter.
  3. Disconnect the exhaust pipes from the catalytic converter (you may need to cut the old exhaust if it is rusted).
  4. Install the new catalytic converter, ensuring proper alignment with the exhaust system.
  5. Secure the new converter with bolts and torque to manufacturer specifications.
  6. Reinstall heat shields or brackets if applicable.

4. Clear Codes and Test

• Tools Required: OBD-II scanner.
• Sub-steps:
  1. Reconnect the negative battery terminal.
  2. Start the vehicle and allow it to reach operating temperature.
  3. Use the OBD-II scanner to clear the P0420 code.
  4. Monitor the vehicle’s performance and check for any reoccurrence of the check engine light.