19th Mar 2010, 19:06

Your most likely problem probably IS the gas cap. When you tighten make sure it clicks a few times (no, that clicking isn't going to break it...)

And there is no way of knowing if you're looking at a big repair cost without knowing what the diagnostic trouble code is (a diagnostic trouble code is thrown by the ECU when one of the engine's sensors detects a problem. The CHECK ENGINE light is shown when one of these trouble codes is present.)

To find out what's wrong, have a mechanic scan the ECU with a scan tool to find out the trouble code. Some scan tools will tell you the problem outright, others will just show the code given by the ECU, leaving you to decode it. Usually these codes can be found on AllData, but your mechanic should be able to tell you the problem by doing that.

If you don't want to do that, go down to your local autoparts store and have them scan it. They will only give you the code however.

The problem doesn't necessarily have to be in the engine itself for the CHECK ENGINE light to turn on.

29th Apr 2013, 05:25

It can be lots of things, and it can happen to a 100k car with as little as 10,000 miles. It needs to be scanned. I had one of my 2 check valves that were sticking in my domestic. Not an engine.