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

Solution

1. Preparation

• Gather tools and parts needed for repair.
• Disconnect the battery to prevent electrical shorts.
• Raise the vehicle securely on jack stands.

2. Inspect and Replace Oxygen Sensors

1. Locate the Oxygen Sensors: Identify the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
2. Remove the Sensors: Use an oxygen sensor socket to carefully unscrew and remove the sensors from the exhaust system.
3. Inspect the Connectors: Check the electrical connectors for corrosion or damage. Clean or replace if necessary.
4. Install New Sensors: Apply anti-seize compound on the threads of the new sensors, then install them into the exhaust system and tighten to the manufacturer's specifications (typically around 30 lb-ft).
5. Reconnect the Battery: Reconnect the battery terminals securely.

3. Inspect and Replace the Catalytic Converter (if necessary)

1. Remove Exhaust Components: Use a socket set to unbolt and remove any exhaust components obstructing access to the catalytic converter.
2. Inspect the Catalytic Converter: Check for physical damage or signs of clogging, such as a rattling sound.
3. Install New Catalytic Converter: Position the new catalytic converter in place and secure it using the original bolts, torquing them to the manufacturer’s specifications.
4. Reassemble Exhaust System: Reattach any removed exhaust components, ensuring all gaskets are new and sealed properly.