i thought that the warning is set up in the programming of the car - you can program the gong ON or OFF, the warning text on the dash ON or OFF, as well as the little icon...

the programming does not change all of by itself - there should be an event, like someone actively changes the values (i did on mine), or the car went to dealership and the dealer's computer reset everything to factory values (factory values differ from country to country, so what is norm in the US could be optional in EU).

have you just noticed the change or it was like this all the times?