My jeep will start up and dies 3 seconds latter. RPM's don't move and while I press on the gas pedal I cannot get it to run longer than 3 secs no matter what. Also it is not throwing trouble codes and does not scan.

 

Sounds to me like the immobilizer part of the alarm system is still engaged. Usually it will die as soon as you let go of the key. In your case, it may be the injectors aren't turning on but they must be giving the starting shot. Try swapping the ASD relay with a headlight relay.

 

I agree with the immobilizer. if there is a problem with your key, after you start your Jeep, the security light will keep flashing and then it will shut the engine off because it doesn't recognize the key. If you have another key, try to see if that key will start it and keep it running. If that doesn't work, there may be something a miss with the sensor that recognizes the key. I found this out when I was programming 2 new keys for my 2001 GC WJ.

 

I'm having the same problem. I'm actually stuck at work at this moment because it won't start. It had done this to me before... A lot. Usually I can wait about 30 min and then it will start right up sometimes I have to let it sit over night then it will start up. If you figure out what the problem is please post because I am clueless.

 

One thing that I was thinking about is when you do have it running you should check the relays in both boxes to see if any of them are getting hot. If you do, I would suggest replacing that relay and then check them again when you have it running. I had a Cherokee that had a bad fuel pump relay, it got hot, and shut down and the Jeep died. Went and bought a new one and never happened again.