Try unplugging the maf. That will put the computer into speed density mode. Doubt it will work but its worth a try.

It really seems like a crank or cam position sensor. That tells your pcm when to fire fuel and spark. I also think the cps tells the pcm to activate the fuel pump.

 

The cranking RPM from the scanner data you mentioned seems low, I would suspect a sensor as well.

If I recall, it should be almost double that.

 

We already tried unplugging the maf sensor and it didn't work. When a truck goes into a security mode does it kill fuel and spark? Or just fuel? Voltage at the ignition switch is in check and there is a voltage drop on the ignition switch too when cranking.

 

I really hope it is just one of the sensors. I'm waiting on my friend to get back but supposedly we can run a test through the scanner for the crank position sensor.

 

Oh and would the crank position sensor cause the fuel pump not to prime? Cause it doesn't do that either unless I jump the relay.

 

Here is a really dumb basic question.... Have you checked all of the ecm, ign, seo and any other fuses? Do you have 12v at the battery?? Also have you checked your ground wires?? Fuel pump doesnt actually come on to prime until the ecm sees a crank signal, the 160rpm ckp signal is extremely low, and may not be enough to get fire or fuel..... Case in point, my truck everytime fuel pump goes out i have a fuel drain back issue for a period of time before the pump goes, what will happen is i will go to start the truck she will crank just fine, and if i keep cranking she wont ever start! But, if i crank it for a couple of seconds, turn it off for about 10 sec and crank it again she will fire right up! Fuel pump primes while the key is off for the 10-20 whatever seconds it is.... I have seen it on multiple gmt800 trucks and suvs.... Usually ends up being a real quick fuel pump diagnosis and replacement!!!

 

No question is dumb at this point lol but yes I have 12v at the battery and checked every single fuse on the truck and continuity with them is good and we tested the grounds on the PCM and if checked out good a long with the fuel pump grounds along the frame.

 

Leaning towards a ckp sensor or something with security, but ore likely the ckp sensor....

 

Hopefully that's it. It's just strange the gas gauge doesn't work either. If that doesn't fix it I may get a tuner to drive out here and turn the security stuff off tomorrow.

 

Does the security light flash when the key is on.... Really keep thinking a ground issue somewhere that seems completely unrelated.... And i know i keep saying this but did you check the fuses in the side of the dash not just the underhood??