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

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the negative battery terminal to prevent any electrical issues.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, wrench set, dielectric grease
• Remove the upstream and downstream oxygen sensors using the O2 sensor socket.
• Inspect the wiring and connectors for damage; replace as necessary.
• Install new oxygen sensors, applying dielectric grease to the threads to prevent seizing.
• Torque to manufacturer specifications (typically around 30 ft-lbs).

3. Examine and Replace Catalytic Converter (if needed)

• Tools Required: Socket set, ratchet, exhaust pipe cutter (if applicable), new gaskets
• Remove the exhaust pipes connected to the catalytic converter, starting with the bolts at the flanges.
• Inspect the catalytic converter for any signs of damage or blockage. If damaged, proceed with replacement.
• Install the new catalytic converter, ensuring the new gaskets are placed correctly.
• Torque all bolts to manufacturer specifications (typically 30-40 ft-lbs depending on the model).

4. Clear Codes and Test Drive

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the P0420 code.
• Test drive the vehicle for at least 20 minutes to allow the ECM to re-evaluate the catalytic converter's efficiency.