Why could my "check engine" light be on in my '98 Subaru Leg

Why could my "check engine" light be on in my '98 Subaru Legacy Outback?
I just got the spark plugs & wires changed & it went off for a bit, but came back on. it could occassionally flash before . it also has sort of a ticking sound when it idles. I know I have to get the differential liquid changed doing that this weekend and maybe the timing adjusted, but I would not think that could make the check engine light turn on. it is been on for a while, and I am about done with the list of maintenance those two things are all that is left. the other fluids & filters & whatnot have been changed oh, and a new radiator

any ideas what it may be?

1 day ago
i read someplace can not find it now that a steady light had something to do with emissions or the catalytic converter, and a flashing light was bad, really bad.

If the check engine light is not flashing than the problem is minor. While it most likely a O2 sensor it may just be a glitch. The light can come on if the gas cap was not properly secured.

Before you do anything else attempt to reset the computer. All you must do is disconnect your negative battery cable. Keep it disconnected for about 30 minutes. Then reconnect your battery. This will purge the computer memory and make the check engine light go off. Run your car for some minutes. It may run a little rough for some miles as the computer readjusts itself.

If the light comes back on then you have to get it checked out more. Take it to a dealer or an autoparts store as others suggested. If the light does not come back on you do not have a problem and it was just a glitch.

This was a $90 lesson to me

Check engine lights are typically not for one particular problem, they're typically many. The only way to learn which problem that it's, is to put it a code reader device on the car and hope it indicates the problem. Some are momentary and some latch. trying to crack this by guessing and shotgunning parts is costly.

YOUR CAR PC isn't seeing the correct parameters to preserve its correct emission level . Let a qualified technician scan the car thru its diagnostic link and tell you therefore

most probably a sensor or something to do with emmisions

Your car has a couple of oxygen sensors. One of those may be bad and causing the check engine light issue. Get the codes read at an auto parts store and that should tell you what the problem is.

If the car has over 60,000 miles there is a good chance it is an oxygen sensor. Those should be changed at about that interval.

That ticking sound will generally be there. All three of my suby's have had it.

As for your check engine light, most probably an o2 sensor. Take it to a local shop with obd2 and have them run the codes, should be free to asses the code.