The Ultimate Cry Baby.. The Check Engine light.

Nothing is worse than heading out to the cottage on a Friday afternoon with the car packed full of kids and Nintendo’s than seeing that dreaded check engine light. Well, there is the always fun “I have to go pee” my daughters declare just as we enter the highway but thats another subject all together.

When this light comes on it means that your vehicles on board computer has detected a problem.   The most common fault codes deal with your gas cap.  You see, all cars newer than 1996 have an EVAP system. The Evaporative Emission Control (EVAP) is a re-circulatory system.  The gasoline in the fuel tank splashes around and creates vapour that on cars made before 1996 was just vented to the atmosphere.  Fortunately, we no longer vent this vapour and it is now stored and recirculated within the vehicles EVAP system.

I won’t bore you with the details how this works but briefly there are several sensors, solenoids (switches) and storage canisters that are needed to make this EVAP system work.  Once you are under way, (typically while cruising on the highway) your vehicles on board computer starts a few tests to see if all these components are working properly.   It seals up the system and tries to detect any leaks.  Here is where the problems can potentially start.  If you have neglected to fully tighten the vehicles gas cap after the last fill up then this test will fail due to the gas cap being loose/leaking.  The computer will initiate the test a couple more times and if it continues to fail it will turn your check engine light on.

Warning, Warning.

Now the check engine light being on does not mean for sure that it is a loose gas cap, but only one possibility. (albeit a very common one)  The best solution is prevention, always give that cap an extra 3 clicks when at the fuel pump.