Ford Repair: 2004 Ford Freestar question

Question
Hi Brian,

I have a question about my 2004 Ford Freestar that I purchased a few months ago. The most recent (and worrisome) problem that I am experiencing is with the vehicle shutting off while driving. I will be driving and without any type of warning my vehicle will just turn off. I put the car in park and restart it like nothing happened. There are no warning lights or or any codes. We had a few thoughts about what may be happening so this is what we did in hopes to fix the problem (but it didn't): Replaced the fuel filter, replaced the air filter, replaced the alternator, and replaced the serpentine belt. Back in the beginning of August I was having a different issue that the local mechanic attributed to the computer behind the firewall getting wet, so he sealed that up (Although he did admit that he wasn't sure that he did a good job that if the problem came back I needed to take it to Ford to have them seal the computer). Do you have any ideas on what the problem could be? I just don't want to start paying to replace things that turn out not to be the problem. The mechanic wonders if it's the smartbox. A few weeks ago I was having issues with my doors locking. They would unlock but not lock. He diagnosed that as the smartbox. I asked him if that could cause the shutting off issue and he's not sure. The smart box replacement will cost me $900. Do you think that the smartbox could be the problem? I greatly appreciate any suggestions on what the problem can be.

Thank you,
Have a great night,
Ricki

Answer
So a few questions , when its stalls does it stutter at all and then die and does the instrument cluster go dead or does it stay on and and car dies ? You've definitley covered a lot of the obvious . I would have been leaning towards the PCM getting wet as well. But if you can answer these questions please and thank you.