Ford check engine lights are VERY sensitive and come on for virtually no reason at all. Ours would come on if we went too long between oil changes. It can also be a stopped up vent in the gas cap (I had that happen, like to NEVER found what it was). We've driven Fords for decades, and the mileage champ in our family was one that went 320,000+ miles with virtually zero problems. I loved all my Rangers (I've had 3) and never had a problem with any of them.
I had some of the problems listed above, specifically the dome light problem (I pulled the fuse, but lost 4WD capability) and that "check engine light". Every time I changed the oil or battery, it would go out for about a week. A friend said that it could be the octane rating that was the problem. I originally bought the Ranger in PA. I returned from an overseas assignment (Iceland, USAF), decided to buy a Ranger (brand new and then drove it to New Mexico (Kirtland AFB). The octane ratings back east were 87,89,91 respectfully and out in NM they are 86,88,90. I tried changing octanes to be above the 87 recommended octane, it worked for about a day and then came back on.
For everyones problem with their dome lights, I know most have pulled their bulbs, but there is a better way. Take off the cover, there are three (3) screws that hold up the asembly, remove the back one (the one closest to the back window), put your bulbs back in, and the cover back on. This won't give you courtesy lights, but it will give you reading lights (the black switch). When the switch (on the light itself) is in the center position the (dome) lights are off, and when pushed to either side it lights that side. If yours is the type with no switch on it (some XL models) I guess you'll have to settle for the "no bulbs" solution.
For those with dome lights that won't turn off..
Easy fix! The switch in the door is stuck. Spray some wd-40 in the door latch mechanism in the door (both)
Work the door a few times and the switch will free itelf and work fine.
Going on 2 years since I did that and it has fixed the problem.