this was a head only swap, I did not swap the cam. Anyway, I followed the instructions word for word in the instructions on LS1howto.com What could cause this? Im not familiar with where the oil pressure sensor is or how it gets the signal to the instrument cluster, is it in the block or what? Is there a wiring harness behind the engine that I could have forgotten to hook back up? To remove any doubt, yes there is oil in the car. where do I start?

 

Or you forgot to hook it up. It's pretty easy to forget it because of the tight location behind the intake and in the loop of the brake vacuum hose.