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

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the battery to prevent electrical shorts.
• Allow the vehicle to cool down if the exhaust has been running.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, torque wrench.
• Remove the upstream and downstream oxygen sensors using the O2 sensor socket.
• Inspect the sensors for damage or contamination. Replace if necessary.
• Install new oxygen sensors by threading them into their respective locations, torque to manufacturer specifications (usually around 30-40 ft-lbs).
• Reconnect the electrical connectors.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, exhaust pipe cutter (if needed), gasket scraper.
• Remove any heat shields or brackets securing the catalytic converter.
• Cut the exhaust pipe if necessary to remove the old catalytic converter.
• Clean the mating surfaces of the exhaust system with a gasket scraper.
• Install the new catalytic converter, using new gaskets and torquing the bolts to specifications (usually around 30-40 ft-lbs).
• Reinstall any heat shields or brackets removed during the process.

4. Reconnect Battery and Clear Codes

• Reconnect the battery terminals securely.
• Use the OBD-II scanner to clear the P0420 code from the vehicle's memory.