The National Highway Traffic Safety Administration has launched an investigation of the 2012 Subaru Impreza. According to government documents (PDF), the sensor that determines whether the passenger seat is occupied may have a pattern of malfunctioning and turning off the front air bags.
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Like many of today's vehicles, the Impreza is equipped with sensors to determine whether the front passenger seat is occupied, and if it is, whether the occupant is full-sized or small, or an object like a child seat. If no occupant is detected, the system deactivates the frontal airbag, preventing it from deploying in the event of an accident.
To date, NHTSA has received 26 complaints of the Impreza's passenger-side frontal airbag being deactivated while the seat was occupied. Thankfully, no accidents or injuries have been reported, but obviously, if the airbag were turned off and there were an accident, that could dramatically increase the risk of injury to a passenger. Subaru hasn't yet revealed the number of complaints it has received about the problem or whether they're linked to any accidents or injuries.
In laying out the scope of the investigation, NHTSA mentions that in May 2012, Subaru issued a technical service bulletin for this very issue. While that isn't necessarily damning evidence, it does suggest that the problem has been ongoing and that Subaru has been aware of it.
The investigation is currently in the Preliminary Evaluation phase, the first of NHTSA's three-stage recall process. NHTSA will now work with Subaru to review complaints, remove duplicate filings, and assess how common a problem this might be.
Depending on those findings, the probe could move to stage two, the Engineering Analysis, where NHTSA will attempt to recreate the problem under lab conditions. The results of those tests would determine whether the investigation moves to its third phase, in which NHTSA could request a full or partial recall of Impreza vehicles.