my BMW 3 Series F30/F31 (2012-2019) battery dies overnight when parked

Solution

1. Preparation

• Gather tools: multimeter, socket set, wire brush or battery terminal cleaner, safety gloves, and safety glasses.
• Ensure the vehicle is parked in a safe location with the engine turned off and keys removed.

2. Address Parasitic Drain

• If a specific fuse correlated with the parasitic draw is identified:
  • Remove the faulty component: Disconnect the wiring harness from the component responsible for the draw (e.g., faulty module or light).
  • Test the component: Use a multimeter to check the component for correct operation and short circuits.

3. Clean Battery Terminals

• If corrosion is present:
  • Disconnect the negative terminal first, followed by the positive terminal.
  • Clean the battery terminals and clamp connectors using a wire brush or battery terminal cleaner.
  • Reconnect the terminals, ensuring they are tight and secure.

4. Replace Battery (if necessary)

• If the battery shows signs of aging (e.g., over 3-5 years old or failing voltage tests):
  • Remove the battery hold-down bracket using the socket set.
  • Carefully lift the battery out of the tray, avoiding contact with any terminals.
  • Install the new battery in reverse order, ensuring the positive terminal is connected first, followed by the negative terminal.

5. Final Checks

• After repairs, ensure all components are reconnected properly and there are no loose connections.
• Clear any error codes from the vehicle's computer system using an OBD-II scanner.