Zero Motorcycles is issuing a recall on the 2012 Zero S and Zero DS after receiving numerous reports of sudden motor shut-downs. Zero attributes the problem to the encoder used to read the position of the motor.

According to documents released by the National Highway Traffic Safety Administration, the encoder position signal may drift beyond the limits of the motor controller, leading the controller to suddenly shut down the motor.

Since February this year, Zero received 13 reports of 2012 S models and DS models suddenly shutting down. At first, Zero believed the problem was caused by insufficient waterproofing of its battery management system, issuing a recall in July. Zero soon realized something else was going wrong, eventually isolating the problem to the motor/controller timing. A solution was put into place in June, but this later proved to be insufficient.

In September, Zero concluded the problem was with the encoder and programed new firmware for the motor controller to compensate for the encoder drifting beyond expected limits.

Zero dealers will update the firmware for motor controllers on affected units. The recall campaign affects 315 units.

[Source: NHTSA]