[SDPassatT]

Well, my car was "CEL free" for the first 70,000 miles. However, in the past 5,000 miles since then, I have had THREE CEL's. One was an coil pack, one was the Ignition Control Module. And now this one I got this morning in which there are no symptoms, the car is running PERFECTLY (knock on wood

). (And yes, the gas cap is tight.)

So, since this is something I've never personally experienced I was wondering what is the public consensus of the CEL? Are there little "quirks" in the monitoring part of the system itself that would make a light go off for little or no reason?

Could something trip a CEL and then go away? Or do they only come on when something pretty "major" is wrong? I just dont understand how the system itself work, where the sensors are, etc. I'm sure some of you can shed some light on this for me.

Lastly...Anyone in SoCal have VAG-COM software I can plug into? I'll bring

.

*I hope this CEL goes away, I have Xmas presents to buy.*

 

[darisgin]

Re: The science behind the Check Engine light (SDPassatT)

I had mine go on (blinking for a minute, then off) this morning. Last night during a rain/sleet storm, I started the car, moved it in the garage, turned the engine off, so I was not surprised to have a quick CEL this morning.

Did you start/stop a cold engine perhaps?

 

[Andrew]

Re: The science behind the Check Engine light (darisgin)

I had a misfire the other morning, when it was 5 degrees, the car started really rough, was shaking slightly, idling rough and the CEL was blinking. I turned it off, and tried again. Much better start, no rough idling and a solid CEL. After the standard 3/4 cold starts the CEL went away.

I just happen to think that the whole system is really sensitive, and its overly cautious. Besides I'd much rather it have that way.

 

[SDPassatT]

Re: The science behind the Check Engine light (Andrew)

So I'm not the only one. Of course.

How many of you have ever had a solid CEL that went away? I wonder what the percentage of CEL's that go away out of all CEL's is? Hmmmmm......

 

[pass-variant]

Re: The science behind the Check Engine light (SDPassatT)

I've had ton's of friends and associates stop by because of CEL's to have ne check their cars with the VAGCOM (MK III's, IV's, B4's, B5's), and out of say 20-25 people, only about 40% of the CEL's were reoccuring. Cleared them, and told them to take a look, and if it came back we'd check again to make sure it's the same thing, and then look for the problem... only about 40% ever had it come back.

IMO, it's sensitive, and VERY emissions-centric... thus the cold start/start-stop/loose gas cap/secondary air codes occupying most of the problems

 

[flipsauce]

Re: The science behind the Check Engine light (pass-variant)

I recently had one caused by a hill stall (my foot was wet: it slipped. what? what?

). It went away, but not for about 7-8 days. Once it did disappear 1) the car seemed to have a lot more oomph 2) the airbag light came on. Go figure.

 

[SDPassatT]

Re: The science behind the Check Engine light (pass-variant)

<BLOCKQUOTE>quote:<HR>I've had ton's of friends and associates stop by because of CEL's to have ne check their cars with the VAGCOM (MK III's, IV's, B4's, B5's), and out of say 20-25 people, only about 40% of the CEL's were reoccuring. Cleared them, and told them to take a look, and if it came back we'd check again to make sure it's the same thing, and then look for the problem... only about 40% ever had it come back.

IMO, it's sensitive, and VERY emissions-centric... thus the cold start/start-stop/loose gas cap/secondary air codes occupying most of the problems<HR></BLOCKQUOTE>


Now THAT is EXACTLY what I was looking for. Thanks!!!

Anyone else wanna add?

 

[sschragger]

Re: The science behind the Check Engine light (SDPassatT)

My CEL comes on at regular intervals, lasts for a few days, then disappears for a week or so. Been doing this for the past few months, first time was alarmed until I called dealer.

I think it might be caused by a vacuum hose problem which is a factory recall. In the meantime, car runs fine!

 

[Green_Hornet]

Re: The science behind the Check Engine light (SDPassatT)

If you're interested, I have the VAG-COM, I work near where you live unless you've moved to NJ already...drop me a line.

<![CDATA[If you're interested, I have the VAG-COM, I work near where you live unless you've moved to NJ already...drop me a line.

[Modified by Green_Hornet, 1:25 PM 12/12/2002]

 

[RechtsFahren]

Re: The science behind the Check Engine light (SDPassatT)

Yeah, I totally agree with Pass. I've had a solid CEL twice, one after a rough start after the car hadn't been used in a while. I figured the car was just cranky (oh no, a pun!) and it recovered by itself.

Most of the time its just a flaky sensor or a disruption in the vacuum (e.g. loose air filter cover). The usefulness of the sensor often isn't critical and it recovers by itself.

All of this OBD (on board diagnostics) stuff originated with the emissions and it has taken about 20 years to branch out significantly from there. So among the things that will trigger a CEL, like Pass said it is heavily concentrated around emissions sensors that are prone to wigging-out than things that are truly critical to running the car or its longevity. In that case you'll likely get a blinking CEL.

When in doubt, ask yourself if the car runs/drives right? And get VAG-COM. Since people don't change their plugs as often as they used to, if you've got a rich or lean condition that would lead to plug fouling, or whatever, that kind of thing WOULD be reasonably important to catch before the next plug change interval. The VAG will also give you valuable talking points when dealing with the dealer. That's the best $200 you could ever spend on the car IMHO. It will actually save you mucho $ for mods!