With a C-class Mercedes there might be a problem with W203 model, manufactured in 2004-2005, because this is when there was a change of seat occupancy sensor. Not only there was a change of plugs, but more importantly one type of a sensor was replaced with another one that generates a different signal. In that case comparison of the plugs is a very good indicator what kind of emulator will work on your car.

 

 

 

In models manufactured in 2000-2004/2005 there is a seat occupancy sensor with a 3-pin plug:

In models manufactured in 2005-2007  there is a seat occupancy sensor with a 4-pin plug: