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

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

Solution

1. Preparation

• Gather tools: OBD-II scanner, multimeter, socket set, torque wrench, safety goggles, and gloves.
• Ensure the vehicle is parked on a level surface and the engine is cool.

2. Clear Diagnostic Codes

• Connect the OBD-II scanner to the vehicle's diagnostic port.
• Clear the P0421 code and any associated codes.
• Record any additional codes for further analysis.

3. Inspect and Replace Oxygen Sensors

1. Locate oxygen sensors: Identify the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
2. Disconnect the battery: Prevent electrical issues by disconnecting the negative terminal.
3. Remove old sensors: Use a socket wrench to unscrew the oxygen sensors.
4. Install new sensors: Apply anti-seize compound on the threads of the new sensors and install them securely.
5. Reconnect the battery: Reattach the negative terminal.

4. Replace Catalytic Converter (if necessary)

1. Remove exhaust components: Unscrew any bolts or clamps securing the exhaust components to access the catalytic converter.
2. Disconnect catalytic converter: Carefully detach the catalytic converter from the exhaust system.
3. Install new catalytic converter: Position the new catalytic converter and secure it with bolts to the exhaust system per manufacturer specifications (usually a torque value of 30-50 lb-ft).
4. Reattach exhaust components: Ensure all exhaust parts are secured and leak-free.

5. Final Steps

• Reconnect the OBD-II scanner and confirm that the P0421 code has been cleared.
• Start the engine and allow it to reach operating temperature.
• Monitor the engine for any abnormal noises or vibrations.