Computer problem
2002 Ford F150 V8 Four Wheel Drive Automatic 135000 miles

We purchased this truck 4 days ago. It runs perfect, does not miss at all. The service engine soon light came on, on the 3rd day. 2 seperate code readers are not finding any readings. People are saying that the computer is "going bad." Or that the wiring has been messed with, The tape has been unwrapped recently. How can we know what is going on with the computer? What type of repairs/wiring can be done? Any help is greatly appreciated, buyer remorse is setting in!