LS376/480 Mil light problem

[FRANKRAT]

I just finished installation of the LS376/480 crate engine and used the factory wiring harness. The engine runs fine, but after about 1 hours of running the mil light came on. Of course I did not use the VSS connection on the harness, as it is a manual transmission and the gauges use another sensor. The wiring installations from GM says it is not necessary to have this hooked up, could this be the problem? What have been your experience in this type fo problem?

[LCD Gauges]

After one hour of run time, it could be anything. You should scan the port to retrieve the code(s) or you'll be chasing your tail.