The driver's seatbelt has a shoulder belt pretensioner.

The pretensioner sensor also serves as follows.
If the sensor detects a certain predetermined amount of force during frontal or side collisions or rollover accidents, the front seatbelt is quickly drawn back in by the retractor to take up the slack so that the belt more effectively restrains the driver.
When a seatbelt pretensioner is activated, an operating noise will be heard and a small amount of smoke will be released.
These occurrences are normal and not harmful. This smoke does not indicate a fire in the vehicle.
Once the seatbelt pretensioner has been activated, the seatbelt retractor remains locked. Consequently, the seatbelt can not be pulled out and retracted and therefore must be replaced.
NOTE
Seatbelt pretensioners are not designed to activate in minor impacts or in rear impacts.
In the case of rollover accidents: As the curtain airbags deploy, the driver's side seatbelt pretensioner and front passenger's side shoulder belt pretensioner are activated simultaneously.
In cases of frontal collisions, the following components will operate si- multaneously.
For details, refer to "Front passenger's SRS frontal airbag" 1-46.
In cases of side collisions, the following components will operate simultaneously.
Pretensioners are designed to function on a one-time-only basis. In the event that a pretensioner is activated, both the driver's and front passenger's seatbelt retractor assemblies should be replaced only by an authorized SUBARU dealer. When replacing seatbelt retractor assemblies, use only genuine SUBARU parts.
If either front seatbelt does not retract or cannot be pulled out due to a malfunction or activation of the pretensioner, contact your SUBARU dealer as soon as possible.
If the front seatbelt retractor assembly or surrounding area has been damaged, contact your SUBARU dealer as soon as possible.
When you sell your vehicle, we urge you to explain to the buyer that it has seatbelt pretensioners by alerting the buyer to the contents of this section.
WARNING
This could result in accidental activation of the seatbelt pretensioners or could make the system inoperative, possibly resulting in serious injury. Seatbelt pretensioners have no user-serviceable parts. For required servicing of front seatbelt retractors equipped with seatbelt pretensioners, consult your SUBARU dealer.
Front seatbelt pretensioners
Front passenger's seatbeltPreparation tool
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