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

Solution

1. Preparation

• Gather tools and parts.
• Disconnect the battery to prevent electrical shorts.
• Allow the engine to cool down before starting work.

2. Inspect and Replace O2 Sensors (if necessary)

• Remove the O2 sensor from the exhaust pipe using a wrench.
• Inspect the sensor for carbon buildup or damage.
• If faulty, replace with a new O2 sensor, ensuring it matches specifications for the Highlander.
• Torque the O2 sensor to the manufacturer's specification (usually around 30 lb-ft).

3. Inspect and Replace Catalytic Converter (if necessary)

• Raise the vehicle using jack stands and secure it.
• Remove the exhaust pipe bolts using a socket set, ensuring to keep any gaskets for reuse if in good condition.
• Carefully detach the old catalytic converter from the exhaust system.
• Install the new catalytic converter, ensuring proper alignment and fitment.
• Torque the exhaust bolts to the manufacturer's specification.
• Reattach any heat shields if applicable.

4. Clear Codes and Reconnect Battery

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

5. Test Drive

• Start the vehicle and allow it to reach operating temperature.
• Monitor the engine's performance and check for the check engine light to remain off.