Airbag sign on a car's dashboard

Airbag: how does it work, warning light & MOT

30 March 2021, 04:59

Invented in the United States in 1953, your car's airbags ensure your safety: in the event of a collision, airbags will be triggered to protect the driver and front passenger.
Airbags are part of the passive safety elements, limiting the severity of the impact in the event of an accident.

There are several airbags inside your car:

  • Front airbags (on the steering wheel and in the glove box)
  • Side airbags (on the sides and in the ceiling)
  • Curtain airbags (at window level)
  • Knee airbags
  • Inflatable Seat Belt

airbag in a car

ℹ️ How does an airbag work?

When an airbag is triggered, it happens in 5 steps and just 150 milliseconds (or 0.15 seconds).

1 - Detection
2 - Trigger
3 - Deployment
4 - Depreciation
5 - Deflation

The step of detecting an impact is possible thanks to the airbag computer. It is also the airbag computer that will trigger the airbag warning light on the dashboard in the event of a breakdown.
The computer will calculate the severity of an impact. Thus, depending on the intensity of the collision, it will be able to decide which airbags will be deployed and at what level.
When the airbags are triggered, the seat belt pretensioner is also activated. Thus, in the event of an accident, the pretensioner prevents play in the seat belt, creating a resistance effect.

⚠️ The airbag warning light is on

You have just noticed that the airbag warning light is on, but you are not sure what that means? The appearance of the airbag warning light can have several causes.

  • Bad electrical contact
  • Battery problem
  • Airbag computer problem
  • Fault in a presence or shock sensor
  • Belt pretensioner fault

If the airbag warning light is on, we recommend that you carry out a diagnosis in a garage to detect the origin of the problem, and ensure your safety by correcting it.
Once the fault has been corrected, the airbag warning light will go off on your dashboard.

airbag warning light

🛑 Airbag warning light & MOT

During your MOT your vehicle's airbags will be checked.
If your car's airbag warning light is on during your MOT, you will need to schedule a second visit. In fact, this indicator light is considered a major reason to fail your MOT, since it directly impacts your safety.

So before taking your car in for the MOT, have a mechanic do a diagnostic check to find the origin of the problem.

Make an appointment - Diagnosis

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