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

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Replace Oxygen Sensors

1. Locate the O2 Sensors: Identify the upstream (before the catalytic converter) and downstream (after the catalytic converter) oxygen sensors.
2. Remove the Sensors: Use an O2 sensor socket to carefully unscrew the sensors from their respective locations.
3. Inspect the Sensors: Check for corrosion or damage. Replace if necessary.
4. Install New Sensors: Apply anti-seize compound on the threads of the new sensors and install them, tightening to manufacturer specifications (usually around 30 lb-ft).

3. Inspect and Replace Catalytic Converter (if necessary)

1. Visual Inspection: Check for any dents, holes, or discoloration on the catalytic converter.
2. Remove Exhaust Components: Loosen and remove any bolts securing the catalytic converter to the exhaust system using a socket set.
3. Remove the Catalytic Converter: Carefully detach the catalytic converter from the vehicle.
4. Install New Catalytic Converter: Position the new catalytic converter in place, ensuring proper alignment, and secure it with bolts, tightening them to the specified torque (typically around 30 lb-ft).
5. Reattach Exhaust Components: Reconnect any exhaust pipes or components removed during the process.

4. Final Checks

1. Reconnect Battery: Reattach the negative battery terminal.
2. Clear Codes: Use the OBD-II scanner to clear the P0420 code from the ECU.
3. Test Drive: Start the vehicle and take it for a test drive to ensure the check engine light does not reappear.