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

Solution

1. Preparation

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

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, torque wrench
• Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
• Remove the upstream O2 sensor using the O2 sensor socket.
• Inspect the sensor for damage; replace if necessary.
• Install the new sensor and torque it to manufacturer's specifications (typically around 30 lb-ft).
• Repeat the process for the downstream sensor.

3. Inspect and Replace the Catalytic Converter

• Tools Required: Socket set, exhaust clamp tool, torque wrench
• Safely lift the vehicle using jack stands.
• Locate the catalytic converter.
• Disconnect the exhaust pipes from the catalytic converter using the appropriate socket.
• Inspect the catalytic converter for signs of internal failure (e.g., rattling noise).
• If defective, remove the catalytic converter and replace it with a new one.
• Reconnect the exhaust pipes, ensuring all connections are secure and torqued to specifications.

4. Clear Error Codes

• Reconnect the battery.
• Use the OBD-II scanner to clear the P0420 code from the vehicle's computer.
• Start the engine and allow it to idle to ensure the check engine light remains off.