NHTSA Engineering Analysis EA11005

The Office of Defects Investigation (ODI) originally opened the investigation of loss of power steering assist in model year (MY) 2004 and 2005 Mini Cooper as Preliminary Evaluation PE10-038.The investigation was upgraded to Engineering Analysis EA11-005 in May, 2011.During EA11-005 the scope was expanded to include MY 2002 and 2003 vehicles that use the same steering system.The subject vehicles now include MY 2002, the first year BMW sold MINI in the U.S., through mid-MY 2005 covering approximately 109,000 vehicles.The subject vehicles use an electrically driven pump to provide hydraulic pressure to a conventional rack-and-pinion steering gear.A pump, the electric motor, and an electronic control unit (ECU) are housed in a single component BMW calls a Power Pack.The investigation focused on contaminant-induced failure of the ECU resulting in a loss of assist without warning.When assist is lost mechanical steering is retained however increased steering effort is required to keep the vehicle on an intended path.Some consumers reported that restarting the vehicle (cycling the ignition switch) would often reinstate the steering assist.Additionally, and by design, assist can also reinstate during the drive cycle in limited circumstances.The unexpected loss of assist, and/or possibly the reinstatement of assist while driving, may contribute to a loss of vehicle control in certain driving situations.During MY 2005 production BMW introduced a revised Power Pack design (the ECU incorporated a conformal coating of the circuit board) which resulted in a significant reduction in failures.ODI identified 20 reports describing crashes consistent with a loss of power assist event possibly caused by a failure of the Power Pack.Two reports alleged an injury however both were minor in nature and did not require emergency treatment (a subsequent doctor's visit occurred in one case).Ten of these reports described low speed crashes with minimal, or in most cases no property or vehicle d