That doesn't look like a PD engine to me, looks like a common rail.
Maybe a CFF or CFFB? Code should be on the cam cover.
As for the coolant sensor, I think... if you look at passenger/gearbox side of the engine, take off the airbox, underneath the EGR etc pieces should be a junction of the coolant system connected to the engine, at the back of that is where rhey like to put coolant sensors because life can't be simple