OBD II P0015 "B" Camshaft Position -Timing Over-Retarded (Bank 1)

I got the “Check Engine” light on my 2002 Volvo (Ford) S40. My OBD reader revealed the code P0015 “B” Camshaft Position -Timing Over-Retarded (Bank 1). What, if any, ways can I reduce the possibilities of the problem. My “research” shows these to be possible culprits: ?Incorrect camshaft timing

? VCT solenoid valve stuck open

? continuous oil flow to piston chamber

? Camshaft advance mechanism binding

? faulty VCT unit

The first thing I would do, would be to get a repair manual (like Haynes, or Chilton’s) and study the engine section thoroughly. You could, also, get a repair manual online, and/or get help from something like www.alldata.com ($25 fee).