Help

Do you want a good guess? You may have a power problem where one or more critical systems are not powering up (like maybe the PCM itself). The fact that the ODB2 scan tool isn't "seeing" the PCM is an important symptom. Don't ignore it. Will need some tests to determine exactly where to focus.

NOTE, IF the PCM is not powering up, THEN it would be EXPECTED to have a PATS issue. Remember there is an exchange of information between the cluster and PCM to "prove out" PATS.

Do you have a Volt-Ohm meter (VOM) and are you willing to use it? If so I suspect you can fix this yourself.

Have you checked the fuses inside the engine bay and driver's kick panel?

Have you done a visual inspect looking for evidence of rodent or water damage?

Does the cluster display all dashes?

Does the cooling fan turn on at initial key on?

Turn the key on but do NOT crank. Does the fuel pump run at EVERY key on cycle?

Turn the key on but do NOT crank. Using a known good ground test for power at fuse F2.34 and F2.2.

Here's some information to also get you started:

1996+ Crank with no start check list
http://www.allfordmustangs.com/forums/4-6l-tech/336452-1997-mustang-wont-ignite.html#2984838

1999-2004 BJB CJB fuse panel layout:
http://www.allfordmustangs.com/foru...r-swap-wont-fire-please-help.html#post2669271