how to diagnose the P0420 code on my Tesla Model 3 Highland (2024-present)

Solution

1. Preparation

• Tools Required: OBD-II scanner, infrared thermometer, multimeter, smoke machine, basic hand tools (sockets, wrenches).
• Ensure the vehicle is parked on a flat surface and the engine is turned off. Disconnect the battery before starting any repairs.

2. Inspect and Replace Oxygen Sensors

• Sub-steps:
  1. Locate the upstream and downstream oxygen sensors (usually near the catalytic converter).
  2. Disconnect the electrical connectors from both sensors.
  3. Use a wrench to unscrew the oxygen sensors from the exhaust system.
  4. Install the new oxygen sensors and torque to manufacturer specifications (typically around 30-40 lb-ft).
  5. Reconnect the electrical connectors.

3. Repair or Replace Catalytic Converter

• Sub-steps:
  1. If the catalytic converter is determined to be faulty, remove the exhaust components leading to it.
  2. Unscrew the bolts or clamps securing the catalytic converter.
  3. Remove the old catalytic converter and clean the mounting surfaces.
  4. Install the new catalytic converter and secure it with the appropriate bolts or clamps, torquing to manufacturer specifications.
  5. Reconnect any exhaust components removed.

4. Clear Codes and Test Drive

• Sub-steps:
  1. Reconnect the battery.
  2. Use the OBD-II scanner to clear the P0420 code from the vehicle's computer.
  3. Start the engine and allow the vehicle to reach operating temperature.
  4. Take the vehicle for a test drive to ensure the code does not return.