If a Volkswagen ECU needs to be repaired, the first step is to check if the ECU is still functioning correctly. The ECU should be checked for any damaged wiring, loose connections, and if any error codes are present. Then the ECU should be tested with a diagnostic tool to ensure that it is functioning properly. If the ECU is faulty, it will need to be replaced or repaired. If the ECU is repairable, then the parts that are faulty should be replaced. After the repairs have been made, the ECU will need to be re-programmed to get the car running correctly.