My 1999 Outback with 184,000 miles runs like a champ, but I get a check engine warning light from time to time. I make a point of tightening the gas cap, but I still get the light from time to time, but it then goes away for a time. Should I try replacing the gas cap?
There are HUNDREDS of things which can turn on the check engine light! To narrow the choices, YOU need to do something. You need to go to someplace, like an auto parts store, and get the code read. This is usually FREE. Bring the code here for disCUSSion and advice.
Rather than beginning by “throwing parts at it”, you should begin by having the stored trouble code(s) read. Auto parts stores like Auto Zone and Advance Auto will do this free-of-charge. The code(s) will be in the format of P1234. Post back with the codes and several people will be able to give you some direction, based on those codes.
That CEL (check engine light) is just a kid in class waving her hand trying to get you attention because she has the answer. You need to have the codes read. Some places will read them for FREE. Try Autozone or Advanced Auto Parts. Get the exact code (like P0123) not just their translation into English and post it back here.
Regarding warning lights:
if the coolant temp light comes on, shut off the engine ASAP
if the oil warning light comes on, shut off the engine ASAP
if a FLASHING MIL/CEL comes on, shut off the engine ASAP
ASAP means driving to the berm of the highway right now and not waiting for the next exit.
But if the MIL/CEL is not flashing, then it’s not an urgent indicator.