Just bought a 99 GT and I owned an 03 before so im used to being around these cars,but I have a few issues im stumped about. Such as the theft light stays on 97% of the time and if the key is in the switch the key reminder chime goes off til you crank it whether the doors are open or not but there isnt a door ajar light
That PATS has been disabled via tune. That's why the theft light stays on "all the time" because as far as the cluster is concerned the key has not been accepted.
It very well may be possible there are other problems with the PATS system hence why it was disabled in the first place.
As for the key minder. I think the door ajar switch is stuck open. It's a common problem in older Mustangs. Water gets in between the door panels and makes things stick. Take the inside panel off and spray some WD40 in the door ajar switch should fix it right up. The door ajar switch is located near the door claw.
Regarding any "missing" cluster lights. Turn the key on but do NOT crank. All of the cluster lights should light up for the "lamp test". That should answer the question about IF there's a bulb burned out or not. OBTW, it DOES happen. Or the prior owner may have removed the bulb in order to "fix" a different issue.
Okay so I have ironed out most of my problems and I've decided that its time for a gear change, I have 17 inch tires on the car it is a 5 speed and i drive daily about 4 miles on the interstate I'm looking for advise on either 3.73 or 4.10 I want a good pickup because i do go to the track very often but there is times where i may drive to Chattanooga TN which is about an hour from where I live so lets hear some opinions