how to fix P0420 code in Toyota Highlander Fourth Generation (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 battery to prevent any electrical issues during the repair.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, torque wrench.
• Locate the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
• Disconnect the electrical connectors from both oxygen sensors.
• Use the O2 sensor socket to remove the sensors from the exhaust system.
• Install new oxygen sensors, ensuring they are torqued to the manufacturer’s specifications (typically around 30 lb-ft).
• Reconnect the electrical connectors.

3. Catalytic Converter Inspection and Replacement

• Tools Required: Socket set, jack stands, exhaust pipe cutter (if necessary).
• Inspect the catalytic converter for any visible damage or signs of overheating (discoloration).
• If replacement is needed, disconnect the exhaust pipes at the catalytic converter using the socket set and exhaust pipe cutter if necessary.
• Remove the old catalytic converter and install the new one, ensuring proper alignment.
• Torque the exhaust connections to the manufacturer's specifications.

4. Clear Codes and Test Drive

• Reconnect the battery.
• Use the OBD-II scanner to clear the P0420 code.
• Start the engine and let it idle for a few minutes.
• Take the vehicle for a test drive to ensure the engine operates smoothly and the check engine light does not reappear.