how to fix P0420 code in Toyota Highlander Fourth Generation (2020-present)

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery's negative terminal to avoid electrical shorts.

2. Inspect and Replace Oxygen Sensors

1. Remove the upstream oxygen sensor:
   • Tools: O2 sensor socket, ratchet.
   • Disconnect the electrical connector and use an O2 sensor socket to remove the sensor from the exhaust manifold.
2. Install the new upstream oxygen sensor:
   • Apply anti-seize compound to the threads of the new sensor (if required).
   • Hand-tighten the sensor, then use the O2 socket to tighten it to the manufacturer's specification (typically 30-50 lb-ft).
3. Repeat for the downstream oxygen sensor as needed.

3. Inspect and Replace Catalytic Converter

1. Remove the old catalytic converter:
   • Tools: Socket set, torque wrench, exhaust pipe cutter (if necessary).
   • Loosen and remove the bolts securing the catalytic converter to the exhaust system.
   • Cut the exhaust pipes if they are welded and not bolted.
2. Install the new catalytic converter:
   • Position the new converter in place, ensuring proper alignment with the exhaust system.
   • Secure with bolts and nuts, tightening to the manufacturer's torque specifications (typically around 30-40 lb-ft).
3. Reconnect any heat shields or brackets that were removed during the process.

4. Reconnect Battery and Test

1. Reconnect the negative battery terminal.
2. Start the engine and allow it to reach operating temperature.
3. Clear the P0420 code using the OBD-II scanner and take a test drive to monitor for any reoccurrence of the code.