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

Solution

1. Preparation

• Gather the necessary tools and parts.
• Ensure the vehicle is parked on a flat surface, and the engine is cool.
• Disconnect the battery to prevent electrical shorts.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, torque wrench
• Remove the upstream oxygen sensor using the O2 sensor socket.
• Inspect the sensor for damage. If necessary, replace with a new sensor using manufacturer specifications for torque (typically around 30-40 ft-lbs).
• Repeat the process for the downstream oxygen sensor.

3. Inspect and Replace the Catalytic Converter

• Tools Required: Wrench set, jack and jack stands, exhaust pipe cutter (if needed)
• Raise the vehicle using a jack and secure it with jack stands.
• Locate the catalytic converter and inspect for any physical damage or noise.
• If replacement is needed, unbolt the catalytic converter from the exhaust pipes using the wrench set.
• Install the new catalytic converter, ensuring all gaskets are in place and torqued to manufacturer specifications.
• If necessary, cut and reattach exhaust pipes with an exhaust pipe cutter and clamps.

4. Reconnect Battery and Clear Codes

• Reconnect the battery terminals.
• Use the OBD-II scanner to clear the P0420 code and any other related codes.

5. Test Drive the Vehicle

• Start the engine and allow it to idle, checking for any unusual noises or issues.
• Take the vehicle for a test drive to ensure the check engine light does not reappear and that the vehicle runs smoothly.