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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to ensure safety.
• Allow the engine to cool down if it has been running.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, torque wrench.
• Remove the downstream oxygen sensor (post-catalytic converter) using the O2 sensor socket.
• Inspect the sensor for damage or contamination; replace if necessary.
• Install the new oxygen sensor and torque to manufacturer specifications (typically around 30-40 ft-lbs).
• Repeat for the upstream sensor (pre-catalytic converter) if necessary.

3. Examine and Replace the Catalytic Converter

• Tools Required: Socket set, jack and jack stands, exhaust pipe cutter.
• Raise the vehicle securely on jack stands for access to the exhaust system.
• Remove bolts securing the catalytic converter to the exhaust system using the socket set.
• If necessary, cut the exhaust pipe to remove the old catalytic converter.
• Install the new catalytic converter, ensuring proper alignment with exhaust flanges.
• Secure with bolts and torque to specifications.

4. Clear Codes and Test

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the P0420 code.
• Start the vehicle and allow it to reach operating temperature.
• Test drive the vehicle under varying conditions to ensure no codes return.