If I had a bus error and codes stored, will the error come on right away if the problem wasn't fixed after clearing all the codes. Do you have to ride it for a while, like you do for a car before it comes back on?
If this is a U code then that's an internal communications issue. For some reason (possibly low battery) the ECM isn't getting information that it needs or requested. How long it takes to perform the cycle that failed and threw a code is anyone's guess. As a general practice it is NOT a good idea to reset any codes though. The only time you would want to reset a code is if you did a repair that you think fixed the problem. If the ECM throws the same code again then you know your solution failed.
This is just a wild guess but my assumption would be that if there really is a bus error it would throw the code again pretty quickly. You might also want to look around to see what other codes are out there as they may point you to the actual device that wasn't answering up and also caused the bus error code. If the bus was truly dead it's likely the engine would not even start.