Daimler first became aware of the problem in April 2015 after a customer’s report. The company describes the problem:
DAG has determined that in rare cases on certain B-Class electric drive vehicles, the powertrain gateway control unit might send an incorrect signal for a very short duration regarding the status of the high voltage contactor. Should this occur, the vehicle would react to this signal by immediately powering down the electric powertrain unit. As a consequence, the propulsion power would be lost, temporarily immobilizing the vehicle. In such a case, the vehicle can be restarted using the ignition key.
After an internal investigation, the company decided to issue a recall. Electric B-Class owners should start receiving notifications to service the vehicle for an update in December.
Earlier this year, a report came out suggesting that Mercedes doesn’t plan to use Tesla’s drivetrain for the next generation electric B-class.
Here’s the full report from NHTSA: