how to fix U0401 code in Tesla Model S Plaid/Refresh (2021-present)

Learn how to diagnose and fix U0401 transmission communication issues in Tesla Model S Plaid. Step-by-step guide with diagnostic procedures and repair instructions.

Solution

1. Preparation

• Tools Required: OBD-II scanner, multimeter, socket set, torque wrench.
• Ensure the vehicle is parked on a level surface with the engine off. Engage the parking brake for safety.

2. Inspect Wiring and Connectors

• Sub-steps:
  1. Remove the protective covers to access the TCM connectors.
  2. Visually inspect the wiring for fraying, cuts, or corrosion.
  3. Use a multimeter to check the continuity of the wiring from the TCM to the battery.
  4. If damaged, repair or replace the wiring as necessary.
• Ensure connections are secure and free of corrosion.

3. Test the Transmission Control Module (TCM)

• Sub-steps:
  1. Disconnect the TCM from its connector.
  2. Set the multimeter to measure resistance and check for proper ground.
  3. Measure the voltage at the connector while the ignition is in the ON position.
  4. Compare readings to the specifications in the service manual.
• If the TCM is defective, proceed to the next step.

4. Update Software

• Sub-steps:
  1. Access the vehicle's software update menu through the main screen.
  2. Check for available updates specific to the TCM.
  3. Follow the prompts to complete the update process, ensuring a stable internet connection.
• Restart the vehicle after the update is complete.

5. Reinstall and Test

• Sub-steps:
  1. Reconnect the TCM connector securely.
  2. Reconnect the 12V battery and ensure all systems are operational.
  3. Perform a test drive to monitor the transmission behavior.
• Re-scan with the OBD-II scanner to check if the U0401 code reappears.