2016 ford transit custom

hi , i have the following vehicle
ford transit custom 2016
2.0 ecoblue cdti  (105hp)
it has a sid 211 contintental pcm

the vehicle starts and drives ,but no turbo and obviously very low power , i have 3 fault codes as follows

P06A7:16-27    Sensor reference voltage  #B curcuit range/performance    continous memory DTC
P02e8:00-27    Intake Air Flow  A Position sensor curcuit low    continous memory DTC
P2564:00-27    Turbocharger Boost control position sensor A curcuit low  continous memory DTC


I have included the 2 wiring diagrams for the sensors
both sensors are pwm on the 2 motor wires (i dont have a scope to check , but they are not really related to the ref voltage of the included sensors)
sensors 
on the turbo actuator
pin 5  = 0.337v.
pin 4  =   pluggen in 0.2v , unplugged 4.9v
pin 3  = 0.07v 

intake air flow on
pin 1  =  0.337v.
pin 5  =  unplugged 0v ,plugged in  no reading as there is no easy access to the plug or wiring harness (i will get this info how ever)
pin 3  = 0.07v

I would expect 5v on pin 5 for the turbo actuator and 5v on pin 1 of the air intake sensor.

i cannot find any info online for the 5v ref curcuits for the pcm , i have pinned out the pcm to find what is spliced onto the 5v refs.  the same 5v ref is shared with 8 other vrefs, camshaft sensor ,fuel temp sensor etc , the other 3 sensors i checked on the same 5v ref  have the same 0.337v  on the ref pins but no faults codes for low V are set in the pcm , it makes no sense!! 

i did test a few of the sensor grounds and they where 2.56 ohms so i dont think  they are shorted , also checked the earths which where fine , and i wouldnt expect earth problem to drop the 5v ref to 0.337v

how would i continue to trace the issue ? some of the sensors are almost impossible to get at . i was thinking
check the 4 12v inputs into the pcm (all come from the ecu relay and are spliced together)
and at the plug for the pcm with it unplugged i was going to check each sensor for a short to ground using each sensors ground and vref pins..  its the other sensors on the 5v ref being 0..337v that is baffling me , 
thankyou for any advice or help , i have a little knowledge but nothing to the level of you guys!!
thanks martin

id pretty much come to the same method , the connectors pins are fiddley little buggers , dont fancy that ,dont want to introduce new issues , im 50 so shakey hands and shite eyes wont help me here!! i also dont fancy chopping the wires and then making good , i think im going to grab a ecu plug from the scrapyard and plug it in. i can atleast test plug b that way as the power is all coming in on plug a ........ plug a will be more tricky , maybe ill cut those 5v refs on there!!
thanks for the suggestion

an update , i pinned out the ecu to find what was on ref1 and ref 2 , both the turbo actuator and the intake throttle where on 5v ref 2(or along with 8 other sensors etc . the ad blue pump being 1 and dpf press sensor , both these also had .3v for ref but had no codes stored or pending which seemed a little iffy to me. it transpires this vehicle had egr off ,dpf off and ad blue delete done on it......... i put an original clean map into the ecu and found i now had 5v ref dtc for dpf and ad blue(and many other dpf/egr etc dtc's) . finally a startin point . rather than disassemble the van to get at the adblue i decided to start with ad blue sensor 2 (which is on vref 2(b) , sensor 1 is on vref 1(A) ) i snipped the wire coming from a13 on plug 2 at the ecu..... boom 5v ref restored to turbo actuator.... the intake throttle still had low vref of 0.3v , this makes no sense , the intake throttle plug is a nitemare to get to , i did a bit of dissasembled a bit to get access to the plug , once i could take the plu on , i had 5v ref unplugged , i took the throttle body off and boom there was issue 2 the 5v ref pin was bent over , some one had obviously tried to take plug in and out before and as its a struggle bent the pin.... put that right plugged back in and no more dtc for low 5v ref.....

i have put the map back on the van to restore there dpf off egr off ad blue delete back into the ecu and now there is no fault codes and van driving spot on.....

so to conclude the egr and ad blue off had hidden some of the dtc's that where needed to see what was going on with the vehile ,

just thought id update as its a pet hate of mine when ppeople dont take time to say how they fixed on a forum lol.

thanks all,great site