# CEL....then not



## JRB'sOilburningCruze (Feb 25, 2015)

Car info: 2014 CTD with 17K Miles

Last week I was out of town (Vegas, baby Vegas) and I let my son, with my FIL in the car, practice driving so he could take his driver's test. Son practices for a good amount last Tuesday, brings it home and gets a CEL. State of MD will not let you take a drivers test with a CEL on. Son ended up using his grandmother's car (2013 Audi A3 TDI). I get home from Vegas Friday drive the car back and forth to work CEL still on. Saturday errand day, CEL still on. Made an appointment with the dealer to get checked out for Monday morning. Drove some more on Sunday, CEL goes out. Cancel appointment, and as of today light still out. Should I take it in and have them check it out anyway, or should I leave as is?


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## akulahawk (Mar 16, 2015)

I imagine that whatever condition caused the CEL to light is no longer present, and after a certain number of drive cycles/engine starts, the CEL turned off because the underlying code was cleared. I doubt that the dealer will be able to read the computer and discover the reason for the code at this point.

My suggestion is simple. Get yourself a code reader and the next time the CEL lights up, use the reader to retrieve the codes before the computer has a chance to clear it. Some codes will auto-clear within 3-5 engine starts, once the underlying problem is corrected/no longer detected.


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## ChevyGuy (Dec 13, 2014)

akulahawk said:


> I imagine that whatever condition caused the CEL to light is no longer present, and after a certain number of drive cycles/engine starts, the CEL turned off because the underlying code was cleared. I doubt that the dealer will be able to read the computer and discover the reason for the code at this point.


While the CEL may be off, it's still in memory for awhile longer. A scanner should still be able to retrieve it. I think that would be a good thing to do just so you have some idea what happened.

The free scan some parts stores will do may be sufficient.


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## diesel (Jun 8, 2013)

I wonder what your son may have done to cause the CEL. Not saying that's what happened, but you never know.


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## Classy56 (Jul 16, 2014)

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## DrKlahn (Feb 10, 2014)

I had a CEL come on out of the blue on mine. But at the time I recently had to fill up from a station that I'm sure doesn't see a lot of diesel traffic. Topped off the tank with diesel from one of my normal stations and within a day it was gone and hasn't returned in over 6 months. I'm guessing the crappy fuel probably caused a little havoc with the NOx sensors and some good clean fuel straightened it out. So it could be that simple in your case. Like Classy 56 says a scan tool will tell you what triggered it (it will be a code). Since the CEL is off the code should have an H behind it for History (C is for current).


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## gregbonat (Apr 5, 2014)

I have had this happen as well. After getting on highway it seems to clear up. May be wrong, but I also took the battery lead off once and replaced it, that cleared the warning light. Think the emissions system is the weak link in the diesel.


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## JRB'sOilburningCruze (Feb 25, 2015)

gregbonat said:


> I have had this happen as well. After getting on highway it seems to clear up. May be wrong, but I also took the battery lead off once and replaced it, that cleared the warning light. Think the emissions system is the weak link in the diesel.


Agreed. Just ask VW....

I'll get a scan tool and see what the stored code is.


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## KpaxFAQ (Sep 1, 2013)

Just go to advance auto or autozone and they'll read for free


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## dougc905 (May 24, 2015)

I've had my cel turn on and then back off a few times now. Usually from one day to the next. When it stays on, I'll worry.


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## diesel (Jun 8, 2013)

The "on again off again" thing tells me it's probably not really a serious issue. That being said, if you are still under B2B warranty, I would have it looked at to prevent future out of pocket expense.


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