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

Solution

1. Preparation

• Tools Required: OBD-II scanner, jack and jack stands, socket set, multimeter, exhaust system cleaner.
• Safety Warnings: Disconnect the battery before working on electrical systems and allow the engine to cool down before working on the exhaust.

2. Inspect and Repair Exhaust Leaks

• Use a flashlight to visually inspect the exhaust system for any cracks or loose connections.
• If leaks are found, tighten or replace the affected components.
• Use exhaust system sealant if necessary to seal minor leaks.

3. Check and Replace Oxygen Sensors

• Remove the upstream and downstream oxygen sensors using a socket wrench.
• Inspect the sensors for damage or carbon buildup. Clean if necessary, or replace them if defective.
• Torque Specification: Tighten the oxygen sensors to the manufacturer's specified torque (typically around 30 ft-lbs).

4. Inspect and Replace Catalytic Converter (if necessary)

• If the catalytic converter is damaged or blocked, it will need replacement.
• Remove the exhaust pipes connected to the catalytic converter using a socket set.
• Install the new catalytic converter and ensure all gaskets are replaced to prevent leaks.
• Torque Specification: Tighten all bolts to the manufacturer's specifications (usually between 30-45 ft-lbs depending on the model).

5. Reconnect Battery and Clear Codes

• Reconnect the battery terminals securely.
• Use the OBD-II scanner to clear the P0420 code.
• Perform a test drive to ensure the issue is resolved.