In September 2019, the Office of Defects Investigation (ODI) opened PE19-013 to assess the potential safety related effects of a malfunction of the Passenger Sensing System (PSS) in 2012-2013 Model Year (MY) Chevrolet Volt vehicles. Consumers reported that due to a malfunction of the PSS, the air bag system malfunction indicator light (MIL) was activated. Many of the complaints noted the malfunction occurred after the warranty period expired and mentioned high repair costs as a major deterrent to the repair of the vehicle.The PSS sensor mat is embedded in the front passenger seat cushion and is intended to detect child seats and small statured occupants who could be harmed by deployment of the frontal passenger air bag. The PSS may develop a malfunction due to bunching of the sensor mat in the seat trench. The bunching of the sensor mat could cause the mat to repeatedly fold in the same location. Over time, the repeated folding can cause an increased resistance in the sensor mat. An increased resistance in the PSS sensor mat is detected as a fault in the air bag system diagnostic. If this fault is detected, a diagnostic trouble code will be stored in the air bag control unit and the air bag MIL will illuminate.Further, if the fault is detected, the passenger frontal and knee air bags will be suppressed in a crash of sufficient severity to warrant a commanded deployment regardless of the nature of size of the occupant of the front passenger seat.The report counts shown above include only those reports that specifically address the issue covered by this investigation, failure of the PSS sensor mat. Reports alleging only that the air bag light is on with no cause stated, or where a different cause was otherwise identified, were excluded as the air bag light could be illuminated for system faults other than a PSS malfunction.The subject vehicles have been in service for approximately ten (10) years. An analysis of General Motors (GM) warranty data for the subject vehicles, including a comparison with other agency and manufacturer data pertaining to similar occupant detection system failure investigations, indicates the subject vehicles experience a comparatively low complaint rate for this issue given the number of years the vehicles have been in service.GM has instituted a cost reduction program for the repair/replacement of the PSS in the subject vehicles. Based on this cost reduction program as well as:1) a comparatively low warranty rate; 2) no reported injuries, deaths or asymmetric deployments; and 3) the age of the vehicles; ODI is closing this Preliminary Evaluation. The closing of this investigation does not constitute a finding by NHTSA that a safety related defect does not exist. The agency reserves the right to take additional action if warranted by new circumstances.The ODI complaints cited above can be viewed at www.nhtsa.gov under the following ODI identification numbers in a separate attachment.
