how to fix P0420 code on 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 negative battery terminal to prevent electrical shorts.

2. Inspect and Replace Oxygen Sensors

• Tools Needed: O2 sensor socket, torque wrench, multimeter.
• Remove the upstream oxygen sensor using the O2 sensor socket.
• Inspect the sensor for damage or contamination; replace if necessary.
• Install a new upstream oxygen sensor and torque to manufacturer specifications (typically around 30 ft-lbs).
• Repeat the process for the downstream oxygen sensor if required.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Needed: Socket set, torque wrench, exhaust pipe cutter (if needed).
• Disconnect the exhaust pipes from the catalytic converter using the socket set.
• Remove any mounting bolts and brackets securing the catalytic converter.
• Inspect the old catalytic converter for blockages or damage.
• Install the new catalytic converter in the reverse order of removal, ensuring all bolts are tightened to the manufacturer’s torque specifications.

4. Clear Error Codes

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the P0420 code from the vehicle's computer.

5. Test Drive

• Take the vehicle for a test drive to ensure the check engine light does not reappear and that the vehicle operates normally.