Just new to this game......running a 24X LS7 on a LS1 pcm. Generally engine starts & idles well. However occasionally engine refuses to start - backfiring or not firing at all. Sometimes it will take 10 or a dozen goes at turning the key on and off before it goes. Other times just once or twice. Pcm comes up with "camshaft position sensor circuit low", which I am told is a problem with the ground signal wire. I have checked the cam sensor wiring harness and it appears ok. Not sure what do do next???

Being a 24x engine we are running a 2x camshaft timing wheel.