With a scan tool.
There are dozens of codes. Be specific as to what code you are getting.
If it is a U.S. car then it is an OBDII compliant vehicle and the codes can be read with an OBDII scan tool.
You can if it's not newer then a 1998 model. If it's newer then a 98 then you will need a engine scanner to do that.
the service engine light is on due to the fact that there is a problem with your truck, this is confirmed by the way your truck is running. you need to get a engine diagnostic check at an auto shop. may just need a tune-up, or the truck has a bad sensor, or engine woes.
There are literally hundreds of diagnostic codes that would cause the check engine light to come on. Many auto parts stores will check the codes for free and tell you what is needed to fix it.
Have it checked for codes with a scan tool.
There are pages and pages of codes, have it checked by a scanner and then diagnosed from there.
have vehicle scanned to determine the problem and have codes cleared
my check engine light is on on start up truck runs great after wormed up runs rough
try www.haynes.com
HAVE AN AUTO STORE OR SHOP HOOK UP THE OBD2 SCANNER TO SEE WHAT CODES ARE
i have a 1998 ford expedition and i had simaliar to the same problem. does it feel like your loosing power? on my truck it was a misfire on my engine coil i would get that check out