A seat mat (seat occupancy sensor emulator or a child recognition sensor) usually doesn't stop working suddenly. Often the AIRBAG / SRS light switches on only when a passenger sits on a seat or, conversely, it is lit on when there is no passenger and will only switch off when someone sits on the seat. It depends on how the seat mat was firtly damaged. If you have owned the car for a long time, you could have been able to observe symptoms of a faulty seat mat. It is worse if you bought a car with the AIRBAG / SRS warning switched on. In such a case it is much harder to assess if the problem was caused by a seat mat, because you were not able to observe symptoms of a faulty seat mat.

It is especially difficult to diagnose the problem if the AIRBAG / SRS warning was lit on for a long time.

Example:

Someone drived a car and AIRBAG / SRS warning lit on. He visited a mechanic, who diagnosed a faulty seat mat. Due to significant costs the owner decided not to replace the seat mat. He drived the car with a faulty seat mat, hence AIRBAG / SRS light on, for  2 years. During that time has occurred some other fault of the SRS system. 

Then you bought such a car and a seller told you that the seat mat is faulty. You installed ant it didn't work. Why? There are the most common reasons:  

1. If the AIRBAG / SRS light was on for a long time, errors can be cleared only with a professional software dedicated to the specific car brand.
2. There occurred some other SRS system fault, not known for the previous owner. He could not be notified about it, since the AIRBAG / SRS light was on all the time (and hence could not switch on again to warn him).

Other common faults of the AIRBAG / SRS system:

BMW

1. Faulty seat belt tensioner: watch the video HERE.
2. Faulty BST (battery safety terminal - a frequent fault in E60 BMW) - learn more
3. Faulty AIRBAG control unit.
4. You own an atypical version of a car. To prepare a working emulator we require to have sent your car seat mat's electronics.

Mercedes

1. There is a different type of a seat mat than was commonly installed in that year. In such a case contact us and we will select a correct emulator. This is the case mostly with:  
   
   • A-class W168
   • C-class W203 (check plugs comparison HERE)
2. You own an atypical version of a car that requires a customized emulator. To prepare a working emulator we need to have sent your car seat mat's electronics. This is the case mostly with:  
   • SLK R 171
   • CLK W208 manufactured in 2005
   • CL C215 manufactured in 2005
   • C W204 - rarely
   • E W211 - rarely
3. Faulty airbag control unit or some other fault. There were cases when a car's computer showed a seat mat error, even though the seat mat worked just fine, sending a correct signal in response to a pressure on the seat.

STILO

There are often problems with a car electric installation. 

MAZDA

Problems occur rarely. Sometimes there are problems with airbag control unit - cold joints.