I'm having one injector that will not fire. I have checked continuity , spark , swapped injectors, changed PCM's ran a jumper wire from PCM to injector, ran jumper from 12V supply to injector, verified grounds. I even swapped the pins and injector plugs between #1 and #3. The problem seems to be with the #1 PCM negative output. It's a 6.0L , PCM # 12589462. Could this be caused by the crank position sensor or cam position sensor? This is driving me nuts....Any suggestions?