What else could be done when the service engine now light comes on.
replaced fuel filter
replaced air filter
oil change
plugs and wires
distributer cap and rotor
new brakes (front)
drain/flush radiator and replace thermostat

What am I missing?

does your temp gauge read correctly,if it is bad it will cause the message to come on and stay on.

Pretty sure temp gauge is correct. Reads betweem 185 and 210. Service light doesn't come on all the time. Mostly after it hits 60 mph.

o2 sensor

Where is the o2 sensor located? This is the first truck that I have owned above the year 73.

Thanks, looked it up on the web and found out where to look.

could be throttle position sensor...most definitely it.

Could be many different things...best thing to do is to get somebody to hook up to your truck's computer and have them download the code stored in the truck's computer. It will help tell you where to go next. Otherwise, you could spend alot of $$ trying different things.

Remember, when the check engine light comes on, your car computer is telling you that it is receiving a reading from a sensor which it cannot compensate for. Could be ignition, air flow, fuel, exhaust/emission related. There are many possible codes which are stored in computer memory which could result in the check engine light to be set. In some vehicles, having a bad gas cap can cause that light to come on.

i agree scout 192.. your local auto parts store will read the codes for you for free in most cases

+1 scout192

Autozone will for free

Mine had a code 34 low egr reading. Most of the time it is carbin build up in the intake.