Volvo Repair: 1998 volvo s 70 t5, volvo s 70, crank shaft

Question
my check engine light keeps going on and staying on.  My local volvo dealer has said that his computer read out shows that the crank shaft sensor is faulty.  He has replaced it twice already and re-set the light switch but it still comes back on and shows the same problem.  The car has just had a complete tune-up and nothing else is showing up as a possible fault.  
The car does seem to lose power at times and hesitates as though no gas is feeding through but then it rides normal again.
Can you offer any suggestions?  I'm about to give up.

Thank you,

R. Mistriel

Answer
without knowing the exact code it is hard to say what is happening .if it is giving the same code then there could be a problem in the control unit or in the wiring harness.I have not seen repeat engine speed sensor codes.I will see if there are any bulletins for this at work monday.sorry I could not help more.