Vanashing CEL light

**04_A4_1.8T** · 10-06-2008 08:31 PM

ok so about a week ago the CEL light turned on in my car... is sounded and behaved fine might have been a "bit" more aggresive.. i decided to have the code pulled at a shop and was driving there and the light went away

this is the second time that this has happened? anyideas what it could be? i am running a giac chip with bigger injectors and nothing else...

**Mark** · 10-06-2008 08:39 PM

find a VAG-Com near you. It could be lots of things, but whatever it is it seems intermittent for you. However, it usually means some part is on the way out. My guess is either an emission (O2 sensor) or an air flow meter issue (lean or rich). Just a guess though . . . like I said , could be lots of things.

find a local vag-com with this page . . . http://www.vagtoolfinder.com/

**04_A4_1.8T** · 10-06-2008 08:49 PM

i have replaced one o2 sensor and 3 coils already... i checked for a vagcom and there wasnt any in utah

...

**Mark** · 10-06-2008 08:54 PM

might want to consider buying one. The initial cost sucks, but I can say quite honestly that I've saved more than the up-front cost of the VAG-com by knowing what is wrong with my car and fixing it myself.

**04_A4_1.8T** · 10-06-2008 09:13 PM

Originally Posted by Mark

might want to consider buying one. The initial cost sucks, but I can say quite honestly that I've saved more than the up-front cost of the VAG-com by knowing what is wrong with my car and fixing it myself.

i have looked into it... i am trying to put it off till christmas that way its free for me but if this keeps up i might just have to jump the gun... i also wanna do that fog light vag...

**Mark** · 10-06-2008 09:20 PM

with the 2002, one of the first vag-com 'tunes' I did was the independent fog-light on. for MY 2003+ you have to change it to Canadian settings and run daytime running lights to have the fogs on by themselves. 2003+ don't allow independent fogs with the switch. I also changed the car to lock at 10mph and a few other things I can't remember . . . windows closing with key-fob. I would definitely recommend the vag-com . . . I've had a lot of people email me to help them out in my area.

**04_A4_1.8T** · 10-06-2008 09:22 PM

i have a 2004 do you know what all it would change if i did the fog mod then?

**Mark** · 10-06-2008 09:24 PM

Originally Posted by 04_A4_1.8T

i have a 2004 do you know what all it would change if i did the fog mod then?

you would have to run daylight running lights . . . which uses the fog lights as the daytime running lights. I am almost positive the setting is Canadian region, I did this to my sisters A4 . . . mostly for safety for her . . . she isn't the best drive out there. Turns out she likes the way it looks too . . .

**04_A4_1.8T** · 10-06-2008 09:33 PM

i read in another post that it turns on the interior lights? i dunno if i like that idea... i think since i have 3000k yellow fogs i will like it...

**martini** · 10-07-2008 07:29 AM

in order for the CEL to turn on, a diagnostic has to fail one or two times (depending on how the diag is typed, A or B). Then the CEL will stay lit until the diag passes 3 times with no failures in between. This has to be on atleast 3 different key cycles.

sounds like you have some intermittent failure.

Even after the diag passes 3 times and the CEL goes off, the code which set the light gets stored in history for the next 30 or so key cycles... so you can still read it with a scan tool

I would suggest scanning codes anyway because you will still be able to get the info from it