Don't know about that, but are you sure about the low pressure side physically?
The reason being I was speaking to a retired Fiat mechanic who mentioned an issue with the instrument panel in regards to false reading of low pressure.
No guarantees , but it may be worth looking into.
As @Kahcorp has stated, the oil pump is in the engine "front" cover. An earlier version of the engine was the 2.3jtd as fitted to x244 models.
I think that the oil pump will only be accessible when engine is removed from vehicle. For the 2.3jtd with engine removed, eLearn lists removing cam belt, crankshaft timing gear, and oil seal, to allow removal of cover. Unless there is a quicker method, access could not be described as simple.