Hyundai Repair: Check engine light 2005 Hyundai Elantra

Question
May check light has come on about three times in the last few weeks.  It is orange in color.  It seems to happen in at the same time.  After leaving work in approximately two miles I have to go down a large hill approximately 3 miles in length.  During this decent the light comes on.  It will stay on for several days.  At first I thought it has to do with the gas cap, but that seems closed properly. After I fill tank light goes out in about 3 days, but this is starting to happen on a regular basis.  My Elantra has 129,000 miles on it, but we have always keeped up with required maintenance.  We live in the country and are quite a distance from a dealership.  I would appreciate any insight you can give me.

Answer
Hi, Karen.  Your check engine lamp simply indicates that the engine control module has detected something irregular.  If the lamp is not flashing and the car drives normally, the problem is likely not critically important; i.e. it's not imperative that you fix it right away.

Unfortunately, the check engine lamp itself doesn't tell us very much about the nature of the problem.  It simply tells us that a problem exists.  In order to get information about the nature of the problem, we need to interrogate the engine control module (ECM), and if appropriate, the transmission control module (TCM) as well.  Once we've received the trouble code(s), we can then begin examining the appropriate system to determine the specific problem.

If you'd rather not go to a dealership, you can take your car to any shop that's reputable in performing what's called driveability diagnosis.  In most cases, chain stores will not be good at this.  Check with your friends and neighbors to see who may be good at this in your location.  

If you'd like, another option is to take your car to the local parts store.  Most offer that they'll read the diagnostic trouble codes for free.  I'll simply caution that you should not accept their diagnostic advice; you're just interested in the code number (typically of the form Pxxxx where x's represent numeric digits)itself.  People that work in parts stores in general do not understand how the car's fuel management and other electronic systems operate and are likely to make a misdiagnosis.  Take the code(s) they give you and report them back here.  This will tell me the nature of the problem, and I'll be able to advise you what to check, or in some cases, what the likely cause of the problem is.