A4 1.9 tdi timing

Apologies for the completely stupid question from a new member, but have an issue with a "misfire" on the engine of a car I am looking to buy, normally around 2000 rpm. Not really bad, manage to go through it OK, sometimes worse than others.
Diagnostic code reads "Camshaft position sensor - signal out of range", is this really the problem or could it be caused by something serious? Also, is it likely to be expensive.
Car has recently had a belt change, although it apparently had the problem before that.
Cheers in advance

I think that was one of the first symptoms on my Passat when its crankshaft pulley was starting to wear on its keyway. Massive job - I would walk away from it. OD

Thanks for the advice, didn't go for that one in the end, although have bought an A4 tdi. Engine seems sweet enough, just have to sort out the usual suspension problems now...