I have a v6 3.8 97 ford mustang the theft light does not come on the dash board, I changed the P.A.T.S module in the ignition,the car cranks right up but shuts off after a sec. can someone help me

reset the CPU by using a code reader . It should reset the immobiliser.

You have a serious wiring issue. No way it will start if engine does not crank. Why isn't the starter turning? Is it good? Is it getting power? if not, did you go to power source and check? start relay?

On the older fords the theft module has 2 plugs in them. You can disconnct one of them, I believe it is the right one , and disable the security system. Finding the module is the hard part. most are located in the middle of the dash.

No there is not a fuse to the crank sensor, and if you were checking for voltage at the crank sensor ,you should see more than 1 volt but less than two volts at the crank sensor positive circuit which is the Dark blue wire, the crank sensor is a hall effect type sensor which generates its own voltage, It would be very helpful to know how this no start problem came about ! was any work recently been perform on your car ? it is also possible that you have a theft type problem with your car, which if for any reason your car"s theft system thinks its possibly being stolen, (example does not like the key or the electronic chip in the key is defective) may put it into to a theft lock down, ford uses different methods to keep the car from been stolen,some are disable the starter (example no crank) another is to disable to fuel pump circuit, or disable the spark,the easiest way to make sure this is not whats the problem, is to monitor your theft light, (located either in the gauge cluster or on top of the dash,) you have a red light or a red key that flashes or possible or just says theft, if the system is working correct when you first turn the key to the run position the light ,key or the theft light will flash three times and then go out and say out if it continues to flash you have a theft problem.there are many other possible reasons why you could have no spark such as broken wires ,wires rubbed bare and grounding out to engine ect, I could help you further but would need more information to help you further ,hopefully this will get you headed in the right direction

Replace ignition.

2 plugs on each side of the motor, under the exhaust manifold center of block you cant miss them. Tap them gently on the sides to turn them, then pry them off. Do not drop them inside the engine thus they are impossible to remove.

If the antitheft light is blinking then the pcm is not getting a signal from the PATS transponder. The Check transponder ring, wiring, PCM fuse in under the hood fuse panel, and lastly pcm. Good luck.

sounds like ecm lost signal from key

Check your battery

The chip is in the key. Either the key has lost it's program or the transceiver is not recognising the key. Try another key if you have one.