stingray454 wrote:
You can't really generalize a steady CEL light as 'no big deal'. There are about 100 different possible error codes that can trigger a steady check engine light. Some are no big deal, others a major deal, or might start out as no big deal but turns into a bigger deal as you drive. For example, the first time my cat were defective, my CEL came on steady, yet it ran OK for about 500 miles. I ignored it, until suddenly the engine started losing power big time, and knocking like crazy under acceleration. Then I brought it into the dealer, and it was diagnosed with plugged and disintegrated cat converters. I was lucky in that my engine was OK, but I have heard of several stories with these defective cats causing complete engine failure due to sucking disintegrated cat material into the engine through the EGR and ruining the cylinder walls. All the while the CEL is on steady. That's just one example - there are many others.

Bottom line is don't ignore any check engine light that stays on, whether its steady or blinking. Ignoring it can do a lot more than just pollute - it can ruin your engine. You should know what the code is before deciding to ignore it.
  This gets to one of my biggest gripes about the whole CEL concept.  The vast majority of the time, a lit CEL indicates something that can be safely ignored for a while.  Rarely, it indicates a serious problem which must be corrected right away in order to prevent severe harm.  Unless you have acess to an OBD-II scanner, you have no way of knowing the difference.  The CEL is a ?Boy who cries ?Wolf!??.  Because it so often lights up to indicate minor problems that can safely be ignored, it is useless as a means of warning for severe problems that require immediate attention.


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Moonlight Blue 1996 Mercury Mystique GS , Zetec engine, ATX.  No mods. (Well, OK, one mod.  Before I got rid of my previous car, a 1994 Tempo, I swapped radios.  I liked the Tempo's radio better.  That counts as a mod, doesn't it?  I also kept one of my Tempo's wheels to use as a spare.  I hate those stupid ?compact? spares that come with modern cars.  Does this count as a mod?  If so, I guess I have two mods.  Replaced burned/melted blower switch and connector on 19 February 2002 with a 1P3T toggle switch from Marvac and a Molex connector from Rat Shack; I guess this now makes three mods.)