how to fix U0100 lost communication with ECM in Tesla Model S Plaid/Refresh (2021-present)

Learn how to diagnose and fix U0100 lost communication with ECM in Tesla Model S Plaid. Step-by-step guide with diagnostic procedures and repair instructions.

Solution

1. Preparation

• Gather tools and parts.
• Disconnect the vehicle's 12V battery to prevent electrical shock.

2. Inspect and Repair Wiring

• Sub-steps:
  • Remove the under-dash panel to access the wiring harness.
  • Visually inspect the wiring for frays, corrosion, or breaks.
  • Ensure connectors are securely seated; reseat them if necessary.
  • If any damage is found, repair the wiring using appropriate techniques (soldering or crimping).

3. ECM Inspection

• Sub-steps:
  • Remove the ECM from its mounting location.
  • Inspect the ECM connectors for corrosion or bent pins.
  • Clean the connectors with electrical contact cleaner if necessary.
  • If the ECM is deemed faulty (no communication), replace it with a new or refurbished unit.

4. Reconnect and Reprogram

• Sub-steps:
  • Reinstall the ECM and ensure all connectors are properly secured.
  • Reconnect the 12V battery.
  • Use a diagnostic tool to program the new ECM if it was replaced, ensuring it matches the vehicle's VIN and configuration.

5. Final Checks

• Sub-steps:
  • Perform a scan to clear any DTCs and check for reoccurrence.
  • Test drive the vehicle to ensure normal operation and verify that communication with the ECM is restored.