Subaru Impreza faces investigation over disabled airbags

The NHTSA inquiry focuses on a potential problem with the occupant detection system for the front passenger airbag.

The National Highway Traffic Safety Administration has opened an investigation into reports of airbag problems with the 2012 Subaru Impreza.

The agency has received at least 26 reports of problems with the occupant detection system, which determines if an adult or child is sitting in the front passenger seat. The complaints allege that the system failed to operate properly, sometimes disabling the airbag when the seat was occupied by an adult.

"In a frontal crash sufficient to warranty deployment, a suppressed air bag may increase the risk of injury to the occupant of the seat," the NHTSA documents note.

Subaru in 2012 issued a technical service bulletin related to the occupant detection system, addressing an apparent issue involving disabled airbags but without handling it as a safety issue.

One complaint claims the issue only occurs when the passenger is sweaty or wearing a wet swimsuit or ski pants, while others claim it occurs when someone is leaning in the seat or only at highway speeds. At least one report alleges complete failure to enable the airbag whenever any passenger is sitting in the front seat.

The 2012 Impreza uses an electrostatic capacitance sensor to classify the passenger, rathe than directly weighing the occupant. Moisture appears to be an inherent issue with such sensors, and several complaints suggest electronic devices on the seat can cause problems.

"When water or anything with high moisture content is spilled on the front passenger seat cushion, the airbag is designed to remain OFF until the seat cushion is dry," a Subaru dealer explains on its website. "This will also be the case if the passenger has moisture on their clothing, such as rain-soaked pants or rain gear. In each of these situations, the airbag status may remain OFF even if a passenger is seated."

The NHTSA will likely spend several months assessing the scope of the potential problem before deciding if a recall is warranted.

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