how to fix P0421 code on Tesla Model S Plaid/Refresh (2021-present)

Learn how to diagnose and fix P0421 catalytic converter efficiency issue in Tesla Model S Plaid. Step-by-step guide with diagnostic procedures and repair instructions.

Solution

1. Preparation

• Tools Required: OBD-II scanner, socket set, torque wrench, multimeter, exhaust gas analyzer.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the vehicle to cool down before working on the exhaust system.

2. Inspect and Replace Damaged Components

• Inspect Catalytic Converter:

  • Visually check for dents, cracks, or rust.
  • If damaged, proceed to replacement.

• Replace Catalytic Converter:

  1. Raise the vehicle and secure it on jack stands.
  2. Remove the heat shield (if applicable) using a socket set.
  3. Disconnect the exhaust pipes from the catalytic converter by removing bolts.
  4. Remove the old catalytic converter.
  5. Install the new catalytic converter and torque bolts to manufacturer's specifications.
  6. Reattach the heat shield.

3. Oxygen Sensor Replacement

• Replace Oxygen Sensors (if necessary):
  1. Locate the upstream and downstream oxygen sensors.
  2. Disconnect the electrical connectors and remove the sensors using a wrench.
  3. Install new sensors and connect the electrical connectors.

4. Clear Codes and Test

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the stored trouble codes.
• Start the vehicle and allow it to reach operating temperature.