Intermittently, approximately 50% of the time, a passenger sitting in the passenger seat does not trigger the Air Bag signal to "ON". When this state occurs, it persists through the passenger exiting the vehicle and re-entering and through the car being turned off and then back on. However, the problem may go away hours later or the next day when we restart the car. We have not witnessed the air bag suddenly enabling mid-ride and we have never seen the air bag warning light displayed.

The passenger is a full-sized woman. Her clothing is typically dry and there is no cell phone on the seat. (We are aware that there have been reports that moisture and electronics can affect the sensor for the ODS on Subaru vehicles).

We understand that there are current cases under investigation for similar problems in the Subaru Forester.

This has been reported to our Subaru dealer (Michael's Subaru of Bellevue). We have brought the vehicle in for this four times in total, and it has stayed at their facility for a week twice. They have been unable to reproduce the problem.

However, they will verify that on one of the visits the sensor was in the incorrect state (not enabled) when we brought in the vehicle and they read the code. They also saw that the passenger exiting and re-entering the vehicle did not enable the air bag, nor did turning the vehicle off and on again.

Update from Jan 27, 2022: OK, this was fun. It turns out that there is a design issue in the state machine the car uses to figure out if there is anyone in the seat.

My wife uses a seat belt extender. If the seat belt extender is attached to the car before she sits down in the passenger seat, then sometimes the car will decide the seat is unoccupied. Basically they only tested with the seatbelt being engaged after weight is on the seat. If the seatbelt is engaged first (which happens if you leave the seat belt extender attached to the car instead of to the seat belt), then the car can decide that there is no one in the seat and it disables the airbag.