Check Engine light went away

[Ferrahs]

I have a 96 328 and for a while my check engine light has been on and im thinking it was just an O2 sensor or something, so last week i decided to put some injector cleaner in the gas tank and the next day my check engine light turned off...heres the catch, when i turn the car on shouldnt the check engine light come on briefly and then go away, well it doesnt, but everything else turns on and goes away, is the light burnt out, or did the injector cleaner really do it.

[Fadec40]

mostlikely, the light burnt out. It should come on briefly during engine start, if not probably a bad lamp.

[TMac325is]

isnt the check engine light supposed to be on, when you turn the key to the "on" or 2nd position before the ignition.

try putting the key there, and if you dont see the light, its gotta be the light... its just that ive never really heard of those lights burning out

[Ferrahs]

can it or should it be fixed

[BlantonG13]

I'd find a way fix it or get it fixed, say you do get something that really is messed up on your car...aside from it just going kablooey and blowing up or something, how else would you know? Its your early warning system.

[Fadec40]

The light should come on briefly until the car starts. If it doesnt come on at all, it most likey is the light. Unless you have a code reader or other diagnostic tool, it is difficult to determine. I am leaning towards a burnt lamp.

If there was a fault that would normally cause that light to stay on, it would come on and stay on until the problem was corrected. It is possible there is a prob with the OBD

[Ferrahs]

i guess im going to have to find a diagnostic tool, i just really have bad luck at the dealer, but from experiance if something is wrong you can either hear it or feel it, the check engine light is just there to tick you off, personally ive been happy this past week not seeing that annoying light on.

[bigred318]

way to go with the injector cleaner i put that in along with my new K&n filter my other one was SOOOO BAd ill take a pic! but yeah i can really feel the difference!

David

[Kevin325i]

Try holding the trip rest down for 10 second then turn the key to position one and releasing it. All the lights should light up, if it doesn't probably burnt.

[Fadec40]

Im sure the injector cleaner worked and made a difference, but remember the check engine light can come on for so many different reasons. I have the code reader/reset tool and it has already paid for itself with just one use. I had the check engine light come on, I retrieved the code, replaced the gas cap and that was it. Had I not had the tool, I would have taken the car to the dealer and I could have been told anything and possibly been ripped off. The code reader/reset tool is a good investment, even if you don't do the work yourself. you will at least know the reason for the light. I myself do all the work, but I understand there are those who don't. To those I suggest you either find a mechanic who you can trust, or purchase a fault code reader.

One another thing to keep in mind, there are alot of states now that are using the vehicle's diagnostic port when the car is inspected. So if the check engine light is malfunctioning and you don't know it, your car will fail inspection if it is subject to a diagnostic check.

[Veracity]

I could be wrong, but if the engine doesnt detect the problem after two cycles doesnt it shut the light off?

[Fadec40]

I'm not sure of the the number of cycles, but it will reset. Keep in mind, Ferrahs said the light doesn't come on at all, even when the key is turned to start. When your car starts up, all those light in the dashboard do a self test and then extinguish when no faults are detected. He may not have any problems at all. But that check engine light should come on when the car first starts, or when the key is turned into position.

[robbins6103]

The check engine light should stay on until its reset.

[jack cass]

Originally posted by Fadec40@Jul 16 2004, 11:51 PM
If there was a fault that would normally cause that light to stay on, it would come on and stay on until the problem was corrected. It is possible there is a prob with the OBD

Actually, on some emissions problems the OBDII systems keep the light illuminated for a certain number of drive cycles, either 40 or 60, depending on what the problem is. After that many drive cycles, it will keep the code stored in memory, but turn off the light.

For example, I have a small problem with the evaporative canister. The light stayed on for 40 times that I drove it, then turned off. However, if I take my Peake tool out there, it gives me the exact same code still. For something like cat problems, it will keep the light on for 60 drive cycles. I guess they figure if you don't get it taken care of, then you aren't going to until you need to pass inspection. Other things like a loose gas cap though, the OBDII turns the light on and off as it's detected.

But anyway, to answer the question on the thread, the light must be burned. It should turn on for a second as you start the car.

(BTW, I have a 96 328i as well.)

[Furious]

Originally posted by robbins6103@Jul 17 2004, 12:28 PM
The check engine light should stay on until its reset.

no not neccesarily, i had the check engine come on once, and it was gone by the end of the day, it turns out that my fault which was the O2, had come then has since never returned,, how i know? well i did my peddle trick and it came up O2 sensor 4 times in a row , than when it went out i used a Modec to find that the code was there but not present anymore, nor has it come back.. weird, i cant explain it.......trust me ive tried