hi i have seen 2 td4 with the same symtoms when i scoped the cam sensor the trace wasnt switching cleanly ie not switching all the way to ground
the first one i replaced the cam sensor engine started straight up and i retested cam sensor,now switching fully to ground and a nice clean signal.(the replacment sensor is slightly different)
the second one i found the same fault codes set and same scope readings so new sensor fitted to no avail when i scoped the front pump the trace was noisy and the current trace seemed to drop out in segments
the rear pump was also noisy but worse so i changed the rear pump and that did cure the fault but i did recomend that the front pump be changed.
hth martin