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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery by removing the negative terminal to prevent electrical shorts.
• Allow the vehicle to cool down if the engine was recently running.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, torque wrench, penetrating oil
• Locate the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
• Apply penetrating oil to the sensor threads and let it sit for a few minutes.
• Use the O2 sensor socket to remove the upstream sensor first, followed by the downstream sensor.
• Install the new sensors by threading them into the exhaust and tightening them to the manufacturer's specifications (typically around 30 ft-lbs).

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

• Tools Required: Socket set, torque wrench, exhaust hanger removal tool
• If tests indicated a faulty catalytic converter, begin by removing any exhaust hangers securing the exhaust system.
• Detach the catalytic converter by loosening the bolts connecting it to the exhaust manifold and the exhaust pipe.
• Remove the old catalytic converter and install the new one, ensuring proper alignment.
• Torque the bolts to the manufacturer’s specifications (usually around 30 ft-lbs) and reattach any hangers.

4. Clear Codes and Reconnect Battery

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

5. Final Check and Test Drive

• Start the engine and let it idle for a few minutes to check for leaks.
• Monitor the engine performance and check the OBD-II scanner for any reoccurring codes.