how to diagnose P0420 code on Tesla Model S Plaid/Refresh (2021-present)

Learn how to diagnose and fix P0420 catalytic converter efficiency issue in Tesla Model S Plaid. Step-by-step guide with diagnostic procedures and repair instructions.

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a level surface and the parking brake is engaged.
• Disconnect the 12V battery to prevent electrical issues during repairs.

2. Inspect and Clean Components

• Inspect the Catalytic Converter:

  1. Visually inspect for dents, cracks, or rust.
  2. Check for signs of high temperatures (discoloration).

• Clean the Oxygen Sensors:

  1. If the sensors are accessible, remove them using an O2 sensor socket.
  2. Clean the threads with a wire brush; avoid damaging the sensor itself.
  3. Reinstall the sensors and torque to manufacturer's specifications (typically around 30 lb-ft).

3. Replace Faulty Components

• If the Catalytic Converter is Damaged:
  1. Remove the exhaust system components connected to the catalytic converter.
  2. Disconnect any electrical connectors and oxygen sensors attached to the converter.
  3. Replace the catalytic converter with a new OEM or high-quality aftermarket part.
  4. Reinstall all components, ensuring all bolts are torqued to specifications.

4. Reconnect Battery and Clear Codes

• Reconnect the 12V battery.
• Use the Tesla diagnostic tool to clear the DTCs and reset the system.

5. Test the Vehicle

• Start the vehicle and allow it to reach operating temperature.
• Monitor the engine performance and check for any reoccurring codes.