There's quite a few sensors for the cams, likely it's just the sensor has gone. Although if you buy it, first thing you should replace is the high pressure fuel pump (HPFP) cam follower. 30 minute job, £45 for a kit of parts and saves thousands if it fails.
The lack of power, could be quite a few areas that need attention (one of which, and most seriously, is the cam follower) but that doesn't usually throw up a fault code. May be the diverter valve (DV) or pressure control valve (PCV) that are knackered and need swapping, again, 30 minute jobs each.