how to fix P0420 code on my Toyota Highlander Third Generation (2014-2019)

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the vehicle battery to avoid electrical issues during repair.

2. Inspect and Replace Oxygen Sensors

1. Locate the pre-catalytic and post-catalytic oxygen sensors.
2. Use a socket wrench to remove the oxygen sensors.
3. Inspect the sensors for damage or carbon buildup.
4. If faulty, replace with new OEM or high-quality aftermarket sensors.
5. Torque the new sensors to the manufacturer's specifications (typically around 30 ft-lbs).

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

1. Raise the vehicle and secure it on jack stands.
2. Remove the heat shield if equipped, using a socket set.
3. Unbolt the catalytic converter from the exhaust manifold and the exhaust pipe.
4. Inspect the catalytic converter for signs of clogging or damage.
5. If replacement is needed, install a new catalytic converter, ensuring it is compatible with the vehicle's emissions system.
6. Torque the bolts to the specified values (usually around 25-35 ft-lbs).

4. Reconnect and Clear Codes

1. Reconnect the battery terminals.
2. Use the OBD-II scanner to clear the P0420 code.
3. Start the engine and let it idle for a few minutes.