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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Ensure the vehicle is on a flat surface and secure it with wheel chocks.

2. Inspect and Replace Oxygen Sensors

1. Locate Oxygen Sensors: Identify the upstream (pre-catalytic) and downstream (post-catalytic) O2 sensors in the exhaust system.
2. Remove O2 Sensors: Using a suitable O2 sensor socket, carefully unscrew and remove the sensors from their respective locations.
3. Install New O2 Sensors: Apply anti-seize compound on the threads of the new O2 sensors and install them, tightening them to the manufacturer's specifications (typically 30 Nm or 22 lb-ft).
4. Reconnect Wiring: Ensure all electrical connections are secure.

3. Inspect and Replace Catalytic Converter

1. Remove Exhaust Components: If necessary, remove any exhaust components obstructing access to the catalytic converter (e.g., heat shields, exhaust pipes).
2. Remove Catalytic Converter: Unbolt the catalytic converter from the exhaust system using a socket set. Ensure to keep any gaskets for reuse or replace if necessary.
3. Install New Catalytic Converter: Position the new catalytic converter and secure it with bolts to the manufacturer's torque specifications.
4. Reassemble Exhaust Components: Reinstall any exhaust components removed in the earlier steps, ensuring a proper fit.

4. Clear Codes and Test

1. Reconnect Battery: Reattach the negative battery terminal.
2. Clear the Codes: Use the OBD-II scanner to erase the P0420 code from the vehicle's computer.
3. Test Drive: Drive the vehicle for a period (generally 10-15 miles) to allow the computer to monitor the new components and ensure the check engine light does not reappear.