02 Tahoe Not Starting
 

I did a transmission rebuild and fuel pump and fuel line replacement. Also replaced the PCV tube and valve. When I turn the engine over it huffs like it wants to start but it acts like a kill switch is engaging. I don't know how to check that. The Ignition relay is new and functional as I get 50psi fuel pressure throughout crank cycle and power to the PCM. I used a spark tube which connects to the spark plug wire and clips onto the spark plug. I can see timed spark in the tube during the full crank cycle which tells me wires and coils are fully functional. All spark plugs and wires have been installed new for this test. I don't know if a kill switch would kill voltage to Injection A or Injection B fuses during a 3-4 second long crank cycle. I checked injection B voltage at 4 seconds crank and the voltage stayed at 12 volts. I will check injection A tomorrow. Everyone has left for the day. I am wondering if there is a run relay and if its the one on the lower outside of the underhood fuse box. Its a relay in its own encasement.

So I checked all ignition sensors during the crank cycle 2 fuses under the hood and 3 fuses in the cabin fuse panel. All were good. It came down to the injector signal output from the computer. I know the injector circuit feeds off a proper cam sensor feed so I checked the wiring there and it looked fine. I had changed the computer with the same identification tags previously for the wrong reasons only to find that the replacement was not sending injector signals. I put the old one back in and it started and the engine continued to run. Problem solved.