In the larger sense, a LOT of people have had that problem with their BMW.
You have someone read Fault Codes and they give you a number but no Definition & NO Interpretation??!! What is the Definition of that Fault Code? At what mileage & engine conditions (Freeze Frame Data) was that Fault Code saved in DME memory? Is the Fault currently present? Would it set a warning light on the dash? ANY decent scan tool or code reader will give you a general Definition of the code AND some or most of that additional information, and if you are just getting a number, that is NOT helpful. INPA will give you ALL of that info.
Bentley gives the following definition of P16A3 (same as BMW FC 2AB4):
P16A3 | 2AB4 | Internal Control Module Checksum Fault in Non-Volatile Memory.
In simplest terms, that means data received/saved by the ECU "doesn't add up" or is inconsistent/incorrect as compared to what some other saved value/function says it should be.
That may have been a one-time hiccup, transient event, which one would simply clear and check periodically to see if it or any other fault code recurs.
So, before anyone can give you any meaningful advice on what to do next, we need to know answers to these questions:
1) What if any warning lights, SES light, etc. did/do you have on your dash BEFORE you had the "scan" done, and NOW?
2) Did whoever "scanned your car" clear the P16A3 code?
3) What "Scan Tool", device or software was used to "scan your car"?
4) What "Electronic Control Modules" did that person actually connect to and read codes from -- JUST the Engine Control Module (DME)? There are ~ 20 other modules in the car in which fault codes can be saved.
5) What condition, symptoms or performance faults did your car have BEFORE the code was read, and/or does it NOW have?
6) I assume there was SOME warning light or condition of your vehicle that caused you to have the scan done? What was that?
This isn't rocket science, but it is science -- knowledge, and it requires SOME thought and evaluation of data.
George