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

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

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Ensure the vehicle is parked on a level surface and the parking brake is engaged.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Test Oxygen Sensors

• Tools Required: OBD-II scanner, multimeter
• Check the voltage output of both pre- and post-catalytic converter oxygen sensors using a multimeter.
  • If either sensor is out of the specified range (usually around 0.1-0.9V for voltage), replace the faulty sensor.

3. Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, torque wrench, exhaust sealant
• If the catalytic converter is confirmed faulty:
  • Remove the heat shield (if equipped) by unscrewing the retaining bolts.
  • Unbolt the catalytic converter from the exhaust system. Use penetrating oil if bolts are rusted.
  • Install the new catalytic converter, ensuring proper alignment.
  • Torque the bolts to the manufacturer’s specifications (check service manual for specific torque values).
  • Reinstall the heat shield and apply exhaust sealant at joints if necessary.

4. Reconnect Battery

• Reattach the negative battery terminal securely.
• Start the vehicle and allow it to idle for a few minutes.

5. Clear Error Codes

• Use the OBD-II scanner to clear the P0420 code and any other related codes.
• Monitor the vehicle for a few days to ensure the check engine light does not reappear.