If the seat belt tensioners have been deployed as a result of a collision, they must be replaced with new ones (workshop work).
Before working on the belt tensioners, disconnect the ground wire from the battery. After that, the negative terminal of the battery must be insulated to prevent accidental electrical contact.
The unused seat belt tensioner assembly removed from the seat should be stored in a locked safe during long-term vehicle repairs.
The seat belt tensioner assembly and control unit are sensitive to impacts. If they have been dropped from a height of more than 50 cm, they must no longer be installed on the vehicle.
When performing welding work, the electrode clamp of the welding unit must be located directly at the welding site. In any case, it is necessary to disconnect the control unit from the wiring harness.
The inflatable airbag / belt tensioner control unit is located under the center console. In order to avoid disruptions in its operation, it is not allowed to put any objects with magnetic properties near it.
The seat belt tensioner unit and control unit must not be exposed to temperatures exceeding 90°C, even briefly. Damaged or defective components must not be repaired under any circumstances. Components of the airbag/belt tensioner system must not be opened by force. Before each installation, ensure that the battery ground cable is disconnected and the negative terminal is insulated.
Never remove or dispose of the seat belt tensioner yourself. Explosive hazard!
Monitoring the system's performance
The airbag/seat belt tensioner indicator should come on and go out after 4 seconds each time the ignition is turned on.
If the indicator does not light when the ignition is turned on, the system is faulty.
If the indicator does not go out or lights up while driving, this indicates a malfunction of the system. It should be assumed that the airbag/belt tensioner system may not work in a collision.
(The original article is posted on the resource bmwman.ru)