Check engine light Frontier

The light came on because the computer received a signal that was not expected. Or it did not get a signal it expected to receive. You need to have it checked out by a competent repair person.

Was it check engine or service engine soon? My 04 has the SES lite, which is emissions-related, mostly having to do w/ the goddamm gascap! Check engine lites are often Ox sensor related. I've heard Autozone can diagnose it, sell you the part, altho my mechanic said sometimes you really do have to spend the bucks for the OEM.

You can go to Autozone or another place like that and they will pull the code for you for free. Then you can decide where to go from there....

Good luck!