error code 17931

Hi all,

recently, I've bought a second hand GOLF IV 1900 TDI 90hp. I've no
problems with this car, but I've decided to do a dignostic test (with
an obd equipment).
The result has been the error code DTC 17931 "Crash Signal from Airbag
Control Unit range/performance". The Airbag has no error in memory and
it works normally (no light is on). Also cancelling the error from the
memory of the control unit it returns when the test goes on.

Can someone help me, please... what is the problem?

thanks for the interest and sorry for my english.

Giovanni