This truck model is very unreliable. I am replacing something constantly, the truck manages to leak oil, water, even dot 3 fluid for the transmission. I think the check engine light being on constantly comes standard from the factory. The people responsible for designing and producing this truck in 2001 can be thanked for the incredible rise in Toyota, and other foreign truck sales in the US since its introduction into the market due to such notorious unreliability.
I bought the 2001 XLT, 2WD, 4.2, 5 speed in 2004. It's now 2017 and this truck still runs like a clock at 190k miles. The only thing I have ever done is change the oil, and air filter, plus other regular maintenance. This truck owes me nothing, and has paid for itself. I did put new plugs in it at around 100k , new ball joints and all tie rod ends in at around 150k. I get 15mpg city, and 19mpg highway. It is starting to look old-school, so, I priced new trucks, but they offer the same fuel mileage. I have decided to keep what I have paid-off years ago, it only costs me fuel and nickel-and-dime maintenance. The engine and 5speed manual tranny sound like they are new still. The headlights are starting to fog over after 16 years, so I'm going to have to spend $38 on a restore kit. I know that tomorrow I can jump in this truck and drive across the country if I had to, and there would be no issues.
2001 4x4 5.4L purchased in 2001, traded in 2015 for new F-150. Never any problems. Normal repairs - brakes, battery...didn't need front axles until 2014. And that was with a 3" level kit. 14 years of perfection. I hope my 2015 F-150 does as well. That truck will problem give someone another 10 good years. A mechanic at the dealership where I traded it in actually purchased it.