Since people get lots of different codes when their check engine light comes on; this means that those codes are being caused by lots of different problems. So even if someone does post the fix that worked when their check engine light came on; chances will be that whatever caused your light to come on was a different problem. THIS IS BECAUSE THERE ARE SO MANY DIFFERENT TROUBLE CODES. People often seem to oversimplify the literally thousands of different things that can happen to a car; and act as if it is all being caused by the same thing. No wonder other people's solutions do not work on your vehicle!!! This problem is further compounded by errors and omissions in some common code definitions, and by people using poor quality sources for code definitions.
The reality of this is that cars are a lot more complicated than they used to be; and many people just cannot deal with complicated situations. I recently read an article by the man who was the director of NASA's Johnson Space Station during the time the space shuttles were being flown. He said that every week, they received thousands of letters from people who thought they had a better idea of how to run the space program. But most of what these people wrote showed that they didn't even have a clue about what it takes to send a space ship to the moon. Why do people keep taking someone else's medicine when they get sick; since it sometimes kills them? It is because most people are unwilling to acknowledge their limitations. Everyone needs to feel like a hero; and at least fantasize that they know as much or more than everyone else; even thougn it is the opposite which usually is true. Because of this excessive pride and denial; a major portion of the automotive advice on the Internet is not worth what it costs to read it. It is just the blind trying to lead the blind.
The "answer" to your problem probably is that; when a car has gone 120,000 miles; it usually needs to have certain maintenance procedures done; but many people do not even read the maintenance schedule which the company that built their car has found from experience needs to be followed. How many scheduled maintenance procedures have you ignored or overriden on your car. Do you even read the maintenance schedule? I have yet to see a maintenance schedule which is thorough enough to cover all the needed items; and yet owners gripe and complain about how much work even the minimal schedules which are published say has to be done to keep the complicated cars they buy running properly.
This is what you need to do now; which will probably clear up the problems on your car:
1> Replace the fuel filter.
2> Thoroughly clean the mass airflow sensor; using only mass airflow sensor spray on this part, and not touching the internal elements with hands or any tools.
3> Thoroughly clean the interior of the throttle body and the idle air control valve; paying particular attention to the back side and edges of the throttle valve and the bore where it touches.
4> Inspect the spark plug cables at BOTH ends; to make sure that none of the boots are torn or damaged; and that all boots are coated with silicone dielectric grease on the inside edges, and are fully seated in their sockets. Replace the whole plug wire set if any boots are damaged.
5> Disconnect all the electrical connectors from the fuel injectors; and spray the terminals in the male and female connector halves with electrical contact cleaner. Plug and unplug the connectors together several times to scrape deposits and corrosion off the contacts. Pack the cavities in the plugs with silicone dielectric grease if the old grease is depleted. Do the same thing with all the other connectors in the underhood wiring harness.
6> Inspect all the vacuum hoses for cracks, damage, or loose connections. Replace any hose which is loose or damaged.
7> Before doing the next step; you'll probably need to know the security code for the sound system in your truck; as it probably will become locked out and have to be reprogrammed after this step is done. The radio code should be included in the literature which came when the vehicle was first sold. If you do not have this information; the dealership may be able to help you recover it; or if you have an aftermarket sound system, go to the place that services this brand
8> After all of the above procedures are done; disconnect the vehicle battery, and turn all the lights and electrical accessories on while the battery is disconnected. Leave the truck like this for 2 hours; then turn the switches off and reconnect the battery. Then have the computer's memory erased with a code scanner that has code clearing capabilities. Do not try to bypass this essential step. Some parts stores may do it; or a friendly repair shop might, too.
9> The motor will run strangely for the first few miles after clearing the computer; and you should drive it under all modes (light and heavy loads; low and high speeds) in order for the computer to relearn the normal sensor inputs.
10> Buy a large bottle of Chevron Techron fuel system and combustion chamber cleaner (from O'Reilly, Auto Zone, Wal Mart, or Chevron stations), and add it to the fuel tank just before filling the tank with Shell, Amoco, Texaco, or Chevron Premium fuel. It usually takes 50 -75 miles of driving for this unique formula to clean out deposits from intake valve stems. Once you see the difference this treatment makes; consider that cheap or unbranded fuel often causes these deposits to return much sooner than when quality fuel is used.
11> If the problem continues; have the computer scanned for trouble codes, and follow the repair procedure indicated by each code that displays.