Crankshaft and Camshaft Sensors

It could be either of those things, or several others too I suppose. Was proper trouble shooting done before the cam/crank work was done? If you suspect timing chain issues you need to find out for sure and address that because that can destroy your engine if its left unattended. After that the electrical system needs to be gone through. On older cars fault codes and other issues actually originate in deteriorating electrical connections rather than the actual parts that the wires lead to. It's tricky and time consuming work. If you're not up to that task find a shop that is. A tech who understands electrical systems and how to trouble shoot them is worth every penny you pay him.