Came on Tuesday evening, great, right at the holidays. So I had decided (it wasn’t blinking which my mechanic told me means PULL OVER NOW) to have him look at it today. It’s done this 2 other times this year for little emissions things, but I did pass SMOG OK.
But now it’s out.
So did the problem fix itself? (unlikely, no?) Or did the little bulb burn out and I am heading for disaster?
We’ve had this happen on occasion. Sometimes it can be caused by a gas cap not being on tightly. Sometimes it’s a computer burp (yes, that’s the technical term… 
) According to our car guy, who hasn’t steered us wrong yet, if it goes out, don’t sweat it. When it stays on, get it checked.
And to see if the bulb is burned out, when you turn your key to the position just before you start the car, all the lights should come on - if it lights there, you’re good.
I speak not as a mechanic but as a diligent car owner, for whatever that’s worth.
The computer keeps a record of faults which caused the check engine light to come on. Even if it is off now a mechanic can check the codes to see why it had been on.
For certain problems, if the problem actually goes away, the ECU will clear the trouble code if it then sees a certain number of engine starts without that problem being present.
The fuel filler cap is a good example. Evaporative emissions are regulated by the EPA, so having a properly sealed gas cap is important. At engine start, the system pulls a slight vacuum on the fuel tank; if the cap is leaking - maybe you didn’t tighten it all the way the last time you filled the tank - the ECU will know about it. Maybe the next time you fill up, you snug the cap up properly; now the ECU needs to see the engine start 5, 10 or ?? times before it says “OK, there really is no problem with the gas cap” and turns the MIL light off.
Depending on what state you live in, you may be able to go to an auto parts store and borrow their code reader to see what trouble codes there are (many stores will do this because then customers often end up buying the needed part from them). As noted upthread, the ECU may keep a record of recent trouble codes even if they aren’t currently active.
Head on over to an auto parts store. They have a thing you can attach to your car to check the code yourself.
Ours has been on forever. We pretty much ignore it, after checking it several times just to find out it’s the gas cap. Yes, we are taking a risk, but given that the car it on its last legs, if it did just die, we we wouldn’t be overly bummed. We seriously need a kick in the ass to get us to go buy a new car, and having the old one flip over and die would be some great motivation.
You may be able to get the code yourself. Google the make a model and “check engine codes.” What you do is turn the key to “off” and “aux” (ie, don’t start the engine) a certain number of time, usually three or five, and then the light will flash. It’ll do something like this:
flash flash flash PAUSE flash flash
That is 32.
Then you go to a page of codes, which unless your car is only a year or two old, should be online, and look up code 32. It might say “system too right of too lean,” in which case, you should change you air filter; it might say “coolant temperature,” in which case you should check the radiator fluid level, and change the radiator thermostat.
All these things are pretty easy fixes, but hurt your gas mileage. They also can be things that were worse when it was really cold, and “got better” when the temperature warmed up, but will trigger the light again when it gets cold again.
Really bad things, like the engine overheating, or the oil leaking out, tend to have their own censors, and in cars less than 10 years old, have automatic shutdowns. You can get stranded, but it will save your car. Don’t sweat this too much.
Bolding mine.
Really? “Don’t sweat this too much.” I can see a problem with this. If grandma & grandpa get a leak in the radiator, & the car overheats causing a shutdown to “save the car”, & if they are out in the desert, on a hot summer day, it may be good-bye to the grandparents. The car is saved, but I for one, would rather have the old folks around for a bit longer. Hell, I’ll buy them a different car. If you do not mind the elderly passing, replace them with a young mother of twin infants.
I am assuming that the old folks, and the young lady, are savvy enough to know how to limp the rig home, or at least to a safe place.
Surely there is some kind of “Battle Override” button on the rig to allow one to sacrifice the car to save the folks inside of it, right?
this is only applicable to older (pre- OBD-II) Chrysler vehicles. the key sequence is “OFF-RUN-OFF-RUN-OFF-RUN.” Newer Chrysler cars will display the OBD-II P-code(s) on the odometer display.
what’s the difference between that and driving another mile or so until the engine seizes? They’re still stranded out in the desert.
An OBD reader would tell you for sure, and can be bought for about $20 or borrowed at pretty much any auto parts shop. Plug it in under the dash, turn the key to on, push whatever buttons are needed to force it to do a read. Look up the code(s) on line.
My Odyssey occasionally throws transient codes like “slow response from valve timing solenoid” - meaning that it went from 6 cylinders to 3 or vice versa and the ECU didn’t like how long it took to do so. There are lots of fuel- and emission-based codes, like loose gas cap, that will clear themselves in a few hours. A code read would answer the question even though the light has gone back off.
Did you miss this papagraph; “I am assuming that the old folks, and the young lady, are savvy enough to know how to limp the rig home, or at least to a safe place.” ?
If you did not understand what I ment, I could expand on that a bit.