renault traffic ii 2002 df074 fault?

Hi my traffic has the pre heat light permanently illuminated. plugged in a Dellphi scanner found a few fault codes and managed to repair/remove all faults except Df074 "Boost pressure sensor: short circuit to +12V permanent"
when sensor unplugged the fault changes to open circuit and when substituted with a second sensor from earlier model fault changes to differential pressure fault.
When I try to clear fault the pre heat lights goes off for a second then back on and fault code remains.
van runs ok in normal use but i have a slight misfire or stutter at around 2200 RPM.
can any one offer any advice as to what i should check or do next???
Cheers Dave j