Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Side Impact Sensor (Sis): Description
The release system for the front airbag consists of a SRSCM installed in the middle of the vehicle and two front impact sensor (FIS) which are located in front of the vehicle. Only the SRSCM is capable of releasing the airbags or the seat-belt pretensioner system in the vehicle. In the dialog between the SRSCM and the front impact sensor it is the SRSCM which takes the release decision. The SRSCM is supported in connection with the front airbag function by the two front impact sensor, which act as intelligent acceleration sensors and as such back up the central airbag controller. Both the front impact sensors continuously report the current system status of the vehicle to the SRSCM.
If one of the two front impact sensor reports an acceleration level, the SRSCM must verify the acceleration signal internally by means of a suitable plausibility check. The SRSCM does not release the appropriate airbag unless the result of this verification is positive.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.