Camshaft sensor out of tune?

What is your question?

Check engine light came on and it was due for an oil change, so we took it to get oil changed. Got that done and light was still on so they put it on computer and said something to the affect of the camshaft sensor might be out of tune? We have to take it to repairman to get looked at, but was curious how much it might cost before we go in, just to get an idea? It jerks/idles.