how to fix P0420 code in Toyota Highlander Fourth Generation (2020-present)

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a flat surface and the engine is cool.
• Disconnect the battery to prevent electrical shorts.

2. Inspect and Replace Oxygen Sensors

1. Locate the pre-catalytic and post-catalytic oxygen sensors.
2. Using an O2 sensor socket, carefully remove the sensors.
3. Inspect the connectors for corrosion or damage and clean if necessary.
4. Install new oxygen sensors by tightening them to the manufacturer’s specified torque (usually around 30 lb-ft).
5. Reconnect the battery.

3. Inspect and Replace the Catalytic Converter

1. If the oxygen sensor replacement does not solve the issue, proceed to inspect the catalytic converter.
2. Remove any heat shields or brackets securing the catalytic converter.
3. Unbolt the catalytic converter from the exhaust system using a socket set. Note that some components may require penetrating oil to loosen.
4. Inspect the converter for physical damage or signs of clogging.
5. Install a new catalytic converter, ensuring proper alignment and secure it with the manufacturer’s specified torque.
6. Reinstall heat shields or brackets as necessary.

4. Clear Codes and Test Drive

1. Use an OBD-II scanner to clear the P0420 code.
2. Perform a test drive to allow the vehicle to reach operating temperature and monitor for any reoccurrence of the check engine light.