My 2000 Silverado 1500 5.3 died while idling for a few minutes in a parking lot. Started to run rough for a few seconds and then died. Started back up, but died again after a second or two. Had it towed to a local shop who told me the fuel pump died. I stupidly took their word for it and changed the fuel pump without any further diagnosis, and not surprisingly that wasn't the problem. There's power going to the pump when the key is moved to the on position for the prime, and it goes off after a few seconds which I believe to be correct, but there's no power getting to the pump while cranking. I borrowed an OBD II reader and it had a crank position sensor code, so I went ahead and changed that - still no signal to the pump while cranking.

I'm not sure what to look at next. Any suggestions?