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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to ensure safety while working on electrical components.

2. Inspect and Replace Oxygen Sensors

1. Locate the upstream and downstream oxygen sensors.
2. Use an O2 sensor socket to remove the upstream sensor (pre-catalytic converter).
3. Inspect the sensor for damage and replace if necessary.
4. Repeat the process for the downstream sensor (post-catalytic converter).
5. Reconnect the battery.

3. Inspect and Replace Catalytic Converter

1. If the oxygen sensors are functioning properly, inspect the catalytic converter for physical damage or clogging.
2. If necessary, remove the catalytic converter by loosening the bolts securing it to the exhaust system using a socket set.
3. Install the new catalytic converter, ensuring it is oriented correctly.
4. Tighten the bolts to the manufacturer’s specified torque values.

4. Clear Codes and Test Drive

1. Use the OBD-II scanner to clear the P0420 code from the vehicle's computer.
2. Start the engine and allow it to reach operating temperature.
3. Test drive the vehicle under varied conditions to ensure the repair was successful.