I think you need to look for the cause... it's likely not reporting that the
sensor was faulty, but the
signal from it. This could be owing to lower oil pressure than expected (eg failing pump, blocked strainer), or conversely, oil pressure too high (failing relief valve for example). Changing the oil won't (necessarily) alter these, and replacing the pressure sensor just means a new sensor is sending the same signal.
The warning triangle can be generated by a whole series of things, including the oil pressure not being as expected... see photos of handbook, so along with your fault code that does seem to point in that direction. I'd be looking to read the actual pressure values in real time (which MulitiECUscan can do, but maybe yours can too?)
That's a good code reader (although not, I believe, supported by Foxwell in the UK). However, although all code readers will read codes from all cars (owing to the international standard ODB2 -- On Board Diagnostics, second generation), Fiat (like most other makes) has its own extra codes that can (generally) only be read by a dealer, or using
MultiECUScan on a PC or as a phone app. That oil code is a 'generic' one though that all readers should see and report on correctly. My car had codes cleared by a non-Fiat mechanic when the alternator was replaced (the falling voltage as the battery drained with no alternator charging it stored a huge selection of fault codes!), but they 'missed' Fiat-specific codes stored by the 4x4 system and didn't reset the steering position sensor. I bought
MES (iOS version) to help identify a glow plug issue, and was able to see and clear those other codes on the way past. Car now goes much better, and steers straight too