[BRUTAL]

Nissan has it with Vin like Rodney said, or you pull off the software in the ecu. Jags are the same. You have a partial part number for the ecu, but what is needed is the SOFTWARE version its running and this comes up when you go into communications with the ecu. the ecu is just a computer without software, depending on what you load, depends on what it does. years ago manufacturers made preprogrammed ecu for apps. this gets very expensive and obsolite, so now ecu are generic and the dealer loads the software/programs based upon vin/options/current latest software

 

[BRUTAL]

while it more time consuming, you can send you ecu to Uprev, or buy Osirus and Cypher. then you can do it all through email with Uprev. You can get a base tune based on what you have, then run datalogs driving down the road from idle to redline for full power tune tweeks, and other part throttle runs and cruise. You can end up with a better tune that dyno cause your doing real world driving conditions