[jdl]

If there is an oil pressure switch in the fuel pump circuit, you will have to account for that switch. Might be located at the rear of intake manifold in block.

You can use a testlite across the fuse terminals, if it burns bright with everything turned off, it's going to ground somewhere. You could unplug the pcm, see how the testlite reacts? If the lite no longer burns? If the lite still burns, then you have a short to ground on that circuit and I think the pcm is ok. If you think it is a pcm problem, you have to be sure it wasn't a sensor or circuit problem that caused the pcm problem, or it might cause the same problem in the new pcm.