2010 Ford Transit VM-XXXT 2.4 TDCI. There's a reason we call this the "Ford Tragic". Occasionally the vehicle will not start/crank or it will start cranking and let go half a second later.
If I clear all the fault codes and read them again after it happens I have these same codes each time:
UCU:P2120 "TPS 'D' circuit fault"
P251A "pto switch" (it doesn't have a pto)
U0140 "lost communication with BCM"
U0167 "lost comm with vehicle immobilizer module"
BCM: U300A "ignition switch".
NOW: this is a security vehicle for money/gold transfer and has an extra immobilizer wired in plus relays with the ability to
shut the vehicle down if it is hi-jacked.
I've added some images of tests I have done and some scope patterns. I have a transponder coil reader (good old Aliexpress) and
when it gets a pulse the vehicle starts every time. For some reason much of the time it will come on and stay on constantly 5 seconds after
the vehicle starts. One of my scope patterns shows where it gets the extra pulse to turn that on.
Another image shows where I have scoped either side of the alarm wiring that is cut into the ignition switch to show when it played up
and didn't start, then started and ran fine without me having to do anything else.
Then there's the CANBUS pattern at the OBD plug - I'm wondering why the pattern changes with the ignition off.