Volvo: Tracs ABS light, premature detonation, volvo xc

Question
We own a 98 Volvo XC and it has had more service problmes than any car I have owned

On long trips, 4 hours plus, or in hot weather the Tracs/ABS light will come on yet when taken to the dealer they said the computer registered no problmes.  My parents had an older model Volvo that had a similar problme that preceeded an premature detonation of the air bag!  Scarry.  Any ideas?

Answer
Josh,
It is a known fact that the ABS control units go bad in those vehicles. Usually I am able to pull codes from these cars they are 314 & 324 rear wheel sensors. That will set you back about $550.00. What happens is a crack in the PC board occures and sets codes.