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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to ensure safety.
• Allow the engine to cool completely before starting work.

2. Inspect and Replace Oxygen Sensors

1. Locate the upstream and downstream oxygen sensors (usually before and after the catalytic converter).
2. Using a socket wrench, carefully remove the oxygen sensors.
3. Inspect the sensors for any physical damage or contamination.
4. If faulty, replace with OEM or high-quality aftermarket sensors.
5. Torque the new sensors to the manufacturer's specifications (typically around 30-40 ft-lbs).
6. Reconnect the electrical connectors securely.

3. Inspect and Replace Catalytic Converter (if necessary)

1. If the oxygen sensors are functioning correctly, locate the catalytic converter.
2. Remove any heat shields or brackets securing the catalytic converter.
3. Use a socket set to unbolt the catalytic converter from the exhaust system.
4. Inspect the old catalytic converter for damage or clogging.
5. Install the new catalytic converter, ensuring proper alignment with the exhaust pipes.
6. Torque the bolts to the manufacturer's specifications (usually around 40-50 ft-lbs).
7. Reattach any heat shields or brackets removed earlier.

4. Clear Codes and Test Drive

1. Reconnect the negative battery terminal.
2. Use an OBD-II scanner to clear any codes that were present.
3. Test drive the vehicle for at least 20 minutes to allow the ECU to relearn and check for the reappearance of the P0420 code.