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

Solution

1. Preparation

• Gather all necessary tools and parts.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the negative battery terminal for safety.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, wrench, multimeter.
• Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
• Disconnect the electrical connectors from both oxygen sensors.
• Use the O2 sensor socket to remove the upstream sensor first, followed by the downstream sensor.
• Install the new oxygen sensors in reverse order of removal, ensuring they are tightened to the manufacturer's specifications (typically 30-40 lb-ft).
• Reconnect the electrical connectors.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, jack and jack stands, exhaust pipe cutter (if applicable).
• Locate the catalytic converter in the exhaust system.
• If any physical damage was found during inspection, proceed to remove the catalytic converter.
• Use a socket set to unbolt the catalytic converter from the exhaust system.
• If the converter is welded in place, use an exhaust pipe cutter to remove it.
• Install the new catalytic converter, securing it with the bolts and following the torque specifications (typically 30-40 lb-ft).
• Ensure all connections are sealed properly to prevent leaks.

4. Reconnect Battery

• Reconnect the negative battery terminal after all repairs are completed.