What would the symptoms of a bad map sensor? My 2004 grand Cherokee with a 4.0 was spitting a code for crank position sensor, it would fire up no prob when cold, but when started and turned off numerous times it would struggle to fire, died a couple times while on freeway, and now incant get a start, when I turn the key I get one click(recent starter and relay change), I also changed that crank sensor and I still can't get anything. any insight? From unhooking my battery I can't get an obd scan either

 

What was the exact code for the crank sensor? A code does not always mean to change a part, it's just a clue of where to start looking.

 

Code was p0320 no crank reference signal at PCM

 

That could mean there is a problem with the wiring or even with the PCM. What brand sensor did you install?

 

Unplug the map sensor. If there is a change when its running then its probably good. If no change then itsprobably bad.

 

I have just finished 4 weeks of searching for a simular problem with my -97 ZJ that suddenly would not fire up when warm but started just fine when cooled of.
At firs mine started when cold and died after 7-8 min but after a couple of days it did'nt fire up at all.

Mine had a voltage drop in the electrical conduit to the fuelpump, there was enough voltage to get the pump twisting so you thought you could hear the pump working but it did'nt got power enough to actually pumpkin gas.
The voltage drop was caused by a poor contact between the cable and the relay inside the relay box (think it's named Power distribute center or something like that in english maybe?) took some time to find that
I changed CPS, TPS, Map sensor, ignitions coil, CPU (you get many tips from other Jeep owners meanwhile searching what was the reason for not starting.
Also demounted the gastank and the fuelpump when I discovered that it was pumpkin fuel direct powered from the battery.

 

What's pumpkin fuel? Lol

 

You have to ask Google translate that

 

He's ragging on your english, Jarna! I think you mean pumping fuel.

Back to the original question. If you're only getting one click when trying to start it, there's a problem with power to the starter. Check your battery cable clamps. They are not carrying the current the starter needs. IMHO, replace the ends.

 

I installed "valucraft" from autozone and now I switched it out for "duralast", considering getting one from jeep and trying that, one mechanic told me that aftermarket cps rarely work

 

Factory sensors are more vehicle specific than the aftermarket sensors. Aftermarket sensors are kind of a universal fit to work on a wide variety of vehicles.