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

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the battery to avoid electrical accidents.

2. Inspect and Replace Oxygen Sensors

1. Remove the upstream oxygen sensor:
   • Use an oxygen sensor socket to unscrew the sensor from the exhaust manifold.
   • Disconnect the electrical connector.
2. Remove the downstream oxygen sensor:
   • Repeat the process for the downstream sensor located after the catalytic converter.
3. Install new oxygen sensors:
   • Apply anti-seize compound on the threads of the new sensors.
   • Install the upstream sensor first, then the downstream sensor.
   • Tighten to manufacturer specifications (typically around 30 ft-lbs).
4. Reconnect the battery.

3. Inspect and Replace Catalytic Converter (if necessary)

1. Remove the exhaust components:
   • Loosen and remove any bolts connecting the catalytic converter to the exhaust system.
   • Carefully remove the catalytic converter from the vehicle.
2. Install the new catalytic converter:
   • Position the new catalytic converter in place.
   • Secure it using new gaskets and bolts, tightening to manufacturer specifications.
3. Reinstall any exhaust components removed earlier.