Constant code 12reading won't start just cranks how do I fix it

Hello, there is no code 12 in the reference material I have for your truck. I do not know what engine you have in your vehicle, also. For a vehicle that cranks but will not start, check for fuel pressure at the engine, and spark at the spark plugs. You could also have a lack of -- or too much -- air flow, but more likely, it's fuel or spark related. Please, stop the guessing -- you've thrown a fuel pump in it, a MAP sensor, and are talking about a crank position sensor now. If you can at least find out what you're missing, you can start narrowing down your testing to fewer components. In the long run, it will be cheaper for you!

Code 12 = system pass - NO fault codes are present.