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

Solution

1. Preparation

• Gather tools and parts.
• Disconnect the battery to prevent electrical shorts.
• Safety glasses and gloves should be worn.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, torque wrench
• Remove the upstream (pre-catalytic) oxygen sensor by using an O2 sensor socket and ratchet.
• Inspect the sensor for damage or contamination. Replace if necessary.
• Install the new oxygen sensor and torque it to the manufacturer’s specifications (typically around 30 ft-lbs).
• Repeat the process for the downstream (post-catalytic) oxygen sensor if needed.

3. Replace Catalytic Converter (if necessary)

• Tools Required: Wrench set, socket set, exhaust hanger removal tool, torque wrench
• Remove the bolts securing the catalytic converter to the exhaust pipes using the appropriate socket.
• Use the exhaust hanger removal tool to detach the catalytic converter from the exhaust hangers.
• Inspect the old catalytic converter for blockages or damage, and replace it with a new one if necessary.
• Reinstall the new catalytic converter and secure it with bolts, torquing to the manufacturer's specifications.
• Ensure all exhaust connections are tight and leak-free.

4. Clear Codes and Test Drive

• Reconnect the battery.
• Use the OBD-II scanner to clear the P0420 code from the ECM.
• Start the engine and allow it to reach operating temperature.
• Test drive the vehicle to ensure that the check engine light does not reappear and monitor for any abnormal symptoms.