Well, the P1400 code isn't caused solely by the PCM/PCU. It's a code that pops up when the system detects an abnormality, and this code is shared and copied across all of the major modules that have some form of on-board data storage. Thus, the PCM, TCM, throttle, stability control, and about a dozen other sensors maintain the existence of the P1400 code. So, yes, you can clear the P1400 from the PCM but it will reappear as there is no way to get rid of it permanently. Dodge has never released the full breakdown of the logical pathway in the vehicle system that pertains to how exactly the code is stored. But, what I've seen and know that it's stored in many locations. If you swap the PCM from a modified back to the original PCM, the P1400 code clears and reappears in about 5 minutes. I know from experience. Even then, when your car communicates OTA (over the air) via a UConnect update or a vehicle status update, it uploads a copy of the diagnostic files to Dodge (Ford does the same thing). So, again, assuming you can eliminate the P1400, Dodge already has a copy on your car's VIN that says the P1400 is there. They likely got the file the first time you fired the car up after making the modification if there's an open WiFi around or if you have the car paired with your cell phone.
Dodge service techs MAY be able to remove the P1400 in cases where the PCM may have gone bad and it was replaced. From what I understand, they actually don't do it themselves, instead, they upchannel a service ticket to the Dodge team responsible for data management and they correct the P1400 on the network end, then push an update to your car to clear it out with an admin level command function (I got this data from the service manager at my local Dodge dealer a few years back).
And, with respect, I wouldn't trust a shop that says they can clear the P1400 right after they blew your engine up because they don't understand how these cars work. That's because the P1400 code is generated initially by the hardware change, but in perpetuity by a software script running from a cloud data center in somewhere like Texas with offshore backups 2-3 locations around the world. So, for your shop to actually clear the P1400 permanently, they'd have to be Russian hackers.
And, I've checked into this as well. What if you disable the car's internet wifi receiver so it can never receive or connect for updates? Heh, that throws a P1400 code too.