# Exhaust Warning Light (likely the 'CEL', or 'Check Engine Light')



## Frank N. Stein (Aug 10, 2006)

*Exhaust Warning Light*

My exhaust warning light came on last night on start-up. Drove the car home without noticing any problem. I reaserched the problem from the manual and it mentioned that I should have an EXHAUST WORKSHOP message on the intrument cluster. Started the car this morning and the light was still on but still no message on the instrument cluster. Eventually drove the car to work and did not notice any difference or quirky behavior.
Called the dealer from work and the service rep indicated that it was safe to drive as long as the warning light was not flashing... she gave me an appointment for next Friday.

Is the service rep correct or should I take the car to the shop ASAP? Has anybody here experienced the same thing? 
BTW, I have the V8...


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## murphybaileysam (Dec 29, 2005)

The tech has told me the same thing about an iluminated CEL that I have had for the last 3 months. As long as it is not flashing they think there is no harm in driving it. Once any of them start flashing though you better get it to a dealer!


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## seednik (Sep 6, 2007)

*steady exhaust system warning light*

I have a 2004 W12 with 35k mi and the exhaust system warning light just came on. The manual wasn't of much help. Can anyone explain what this likely means is wrong (if anything) and how long I really have to get to the dealer? I called the dealer and they said it could wait a couple of weeks if needed. (The only Phaeton-certified mechanic at the dealer I've been using has a broken ankle and won't be back until the end of the year. So, I need to know whether to take their advice and bring it in late Dec/early Jan or go to the only other dealer in town (Syracuse NY), who I have no experience with).
Thanks very much for any help.
-Terry


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## vah (Oct 12, 2007)

*Re: steady exhaust system warning light (seednik)*

i have w 12 2004 with 32k on it.
i had the same problem (when i got to 30k). the dealer took it in twice. one time they did a major work, but it did not fix it. on the second time, they changed the gas cap, and the light is off.


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## vah (Oct 12, 2007)

*Re: Exhaust Warning Light (Frank N. Stein)*

what is going on? you are the second person to ask the same question.
i had the same thing, about a month ago. they also told me that if it is not flashing you can drive it.
the solution was, to change the gas cap, and reset the system.
did you keep the car running while filling up gas?


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## Frank N. Stein (Aug 10, 2006)

No, the car was parked for a couple of days before I used it the other day. There was no problem before this one. 
BTW, the fuel guage shows 1/4 full, so I must've filled up a week to ten days ago.


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## car_guy (Aug 19, 2005)

*Re: (Frank N. Stein)*

I've seen a "Gas Cap Loose" or some such warning come up once or twice since I've owned the car so it seems the Phaeton has a specific warning for this condition. So my question is if this condition is causing the other problems mentioned above posts, why hasn't the warning I've seen been displayed? Makes you wonder if in fact it is the cause.


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## car_guy (Aug 19, 2005)

*Re: (murphybaileysam)*


_Quote, originally posted by *murphybaileysam* »_The tech has told me the same thing about an iluminated CEL that I have had for the last 3 months. As long as it is not flashing they think there is no harm in driving it. Once any of them start flashing though you better get it to a dealer!

Some months ago I had a CEL on (not blinking) due to a faulty sensor (I'd have to look up which one) that made the car virtually undriveable. It became difficult or impossible to start, idled roughly, and didn't respond properly to throttle input. I was fortunate to be able to drive it to the dealer.
It is true that most CELs are strictly emission related but some are not and most definitely affect driveability. Two minutes in mine would have convinced anyone. 
Steven


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## Paldi (Sep 4, 2004)

*Re: Exhaust Warning Light (Frank N. Stein)*


_Quote, originally posted by *Frank N. Stein* »_My exhaust warning light came on...
Called the dealer from work and the service rep indicated that it was safe to drive as long as the warning light was not flashing... she gave me an appointment for next Friday.
BTW, I have the V8...

I also have a V8. When it had a CEL problem 2 years ago, the cause turned out to be a melted vacuum hose in the 2ndary air system. The hose got too close to an exhaust manifold and melted just enough to cause a slight leak. The CEL did not flash, it was steady but sometimes turned off by itself after a number of restart cycles. It came back 8 - 10 times before they caught on to it.


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## PanEuropean (Nov 3, 2001)

*Re: steady exhaust system warning light (seednik)*

Hi Terry:
When you refer to the "exhaust system warning light", what icon are you referring to? I have the same year/model/engine car as you, and I am not aware of an exhaust system warning light - only a 'MIL' (Malfunction Indication Light', which was formerly referred to as a 'CIL' (Check Engine Light).
There is a symbol decoder at this post: Phaeton Accessibility for people with physical impairments, decoding symbols. Look up the symbol you are seeing there, and let us know what the name of it is.
Michael


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## PanEuropean (Nov 3, 2001)

*Re: Exhaust Warning Light (Frank N. Stein)*

Hmmm...
Two posts the same day from two different people living in the same region of the country.
Was it exceptionally cold last night? Did you guys park your cars outside? Did you fill up with gas today? If the answers are "yes" to these three questions, then probably the cause of your MIL light (Malfunction Indication Light) illuminating was spurious - it was caused by the air in the air space (unfilled portion) of the gas tank cooling and suggesting to the car that there was a leak in the fuel tank.
Just ignore the light - it is an emission control light, not a 'something is wrong with your engine' light - and see what happens after a few driving cycles and a few days go by. My guess is that the light will extinguish on its own after a few days... it is programmed to do that if the problem does not repeat after a few additional drive cycles go by.
NB that a "drive cycle" is any one engine start/stop sequence that is separated by more than 1 hour 55 minutes from the previous and/or next one/
Michael


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## mlong1 (Dec 6, 2007)

*Re: Exhaust Warning Light (Frank N. Stein)*

Frank,
I bought my Phaeton last weekend. On my way back home to Dallas, TX the CEL turned on. At the beginning there was no performance issue. An hour later the car began missfiring while driving at highway speeds. The CEL was flashing. The dealer here in Dallas has had the car for a week now. Diagnosis indicates that 2 coils are faulty. Apparently these are part of the ignition system. I will post the full diagnosis once I get the car back. My car has 37k miles and is equipped with the V8.
Marcos

_Modified by mlong1 at 9:11 PM 12-7-2007_


_Modified by mlong1 at 9:14 PM 12-7-2007_


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## seednik (Sep 6, 2007)

*Re: Exhaust Warning Light (mlong1)*

This just started happening to my car as well. At highway speeds yesterday on a 2-hour trip, the sputtering started and 6 times the exhaust warning light started flashing. It seems to drive perfectly at city speeds. Sorry to be stupid, but what are the "coils" that you are referring to? The Phaeton people here are a bit slow, so it would be very helpful to be able to point them in the right direction (so I don't have to give up my precious car for a week).

I would appreciate comments from anyone that can shed more light on this. Is the car still safe to drive? Is this thing going to die on the highway one of the times this thing starts sputtering? Am I doing real damage by continuing to drive it?
Thanks.
-Terry


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## PanEuropean (Nov 3, 2001)

*Re: Exhaust Warning Light (seednik)*

Terry:
Only because I know it has been extra-cold in your area lately:
Try removing and replacing the gas cap. It is possible that water may have frozen in the gas cap and plugged the vent hole. This will prevent air from entering the gas tank as you consume the fuel, and would create exactly the same problem that you have described. When you do remove the gas cap, listen carefully to determine if there is a "whoosh" type sound that would be associated with relieving a vacuum within the tank.
It's always least stressful to try the easy solutions first...








Michael


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## seednik (Sep 6, 2007)

*Re: Exhaust Warning Light (PanEuropean)*

Michael
Thanks. Yes, I've had the cap off and on several times and even filled the tank during the trip. Sadly, not the answer. I appreciate the help, though.
-Terry


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## mlong1 (Dec 6, 2007)

*Re: Exhaust Warning Light (seednik)*

Terry,
I will provide the malfunction codes and more details on the "coils" once I get the car back. I have no idea what coils the dealer is referring to so I am just as slow as you on that subject.








Marcos


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## JMMcMullin (Jan 20, 2006)

*Re: Exhaust Warning Light (Frank N. Stein)*

Additional inputs on the non-flashing check engine light. 
It took almost a year to resolve the issue on my 2004 W12 which first occurred around 31k miles (similiar to some posts here). In New Hampshire it was diagnosed several times as loose wires/connections. Each time it cleared but reappeared anywhere from first start-up to several start-ups later or while changing speed. Next diagnosis was failed Oxygen sensors which were replaced over several visits each prompted by a check engine light within 1-2 days of last dealer correction.
Returned car to Texas and Boardwalk Volkswagen, Plano, did a thorough check on the entire car emphasizing that many aspects of engine operation, fuel system, air intake, and transmission performance are inputs to the CEL fault. Initial diagnosis revealed a failed air mass flow controller (W12 has two, one for each 6 cylinder engine). Replaced under CPO warranty (42k miles). For reference the left mass flow controller is for the right engine bank








Steady CEL appeared again in 2 days.
Next vehicle inspection revealed torque converter was operating improperly (no risk to engine or transmission) causing the check engine light due to incorrect gear for corresponding engine operation at some point (probably shifting late or early). Required dropping transmission & exhaust system for replacement of torque converter.
Appears to be resolved now (3 weeks, no light). Another note when I was researching in the Phaeton archives there was a referencing to an exhaust sytem leak causing the CEL alarm.
Additional items to bring up to your tech if the problem lingers.
Jeff


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## mlong1 (Dec 6, 2007)

*Re: Exhaust Warning Light (JMMcMullin)*

Jeff,
Thank you for the information. My car is at Boardwalk Plano as well. Hopefully the guys at Plano get it fixed correctly the first time.
Marcos


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## car_guy (Aug 19, 2005)

*Re: Exhaust Warning Light (mlong1)*


_Quote, originally posted by *mlong1* »_I have no idea what coils the dealer is referring to so I am just as slow as you on that subject.

The coils (aka coil packs) sit on each spark plug and provide very high voltage to the plugs. Not too long ago a car had one coil and it was distributed through the distributor (clever, no?) to each plug.
VW had a major recall recently because of defective coil packs but I don't believe this affected Phaetons.
Steven


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## Motorista (Oct 28, 2005)

*Re: Exhaust Warning Light (mlong1)*

Terry and Marcos,
The Phaeton, like almost all modern cars, has individual ignition coils for each spark plug. In the V8, these are easily visible: they are the black rectangular boxes, each with its own cable, mounted four on each side of the engine, roughly above each cylinder. The spark plug is directly under the coil. If one or more of these were defective, the high voltage necessary for that cylinder's spark would be missing, hence the misfiring (or hiccup). 
In my experience (both with the Phaeton and with other cars) individual ignition coils are very dependable. The probability of one being defective is low, and two (or more) at the same time even lower, imo, so I'm rather puzzled by the diagnosis. Still, the fact that the misfiring was very noticeable does point to more than one cylinder misfiring, since, on a v8, a single misfiring is not that noticeable. Given that, in Terry's case, it happened only at highway speeds would indicate more of a fuel delivery problem, hence Michael's suggestion. I'm also wondering about the quality of the most recent fuel: perhaps lower quality, or a higher than normal ethanol content, or even some contamination: did the problem start after a fill-up, and, if so, was it at your regular station or a new one? Finally, it could be due to a major motor management cpu failure, though that's even less likely.
As for possible permanent damage when running the car under these conditions, consistent lack of combustion in one or more cylinders can cose permanent damage to the cathalytic converter, as well as, eventually, to the engine itself due to the uncombusted gasoline eventually seeping into the oil from the piston rings. This is a worst-vcase scenario, however, and unlikely to have happened yet. Still, I would not continue to operate the car this way, and would chance the oil as a precaution after the repair is completed.
Good luck.
Stefano


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## mlong1 (Dec 6, 2007)

*Re: Exhaust Warning Light (Motorista)*

Stefano,
Thank you for the coil explanation. The failure in my car took place during a trip from Chicago to Dallas roughly 900 miles. It is possible that I got some bad fuel, but given the lengh of the journey, I had to refuel at least 3 times. Will post the final diagnosis once I get the car back next week.
Marcos


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## PanEuropean (Nov 3, 2001)

*Re: Exhaust Warning Light (mlong1)*

You bought fuel in the Chicago area? That is the kiss of death for any W12 Phaeton (seriously). We have had all sorts of discussions in the past about the effects of the very high ethanol Chicago-area winter blend fuel on the W12 engines.
The executive summary is this: Chicago area winter grade fuel has more ethanol in it than the engine is designed to accept.
Try running your engine on a fill-up of nice super-premium grade Texas fuel. There is a good chance that will bring it back to health.
Michael


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## chipmjohnson (Sep 11, 2007)

*Re: Exhaust Warning Light (PanEuropean)*

I also recently had a CEL, which one coil pack was replaced. A few days later a second CEL and another bad coil. The Tech called VW and got authorization to replace the remaining 7 coils. 
Clearly there is an issue here. Hopefully they have done some type of redesign, so these issues won't continue.


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## car_guy (Aug 19, 2005)

*Re: Exhaust Warning Light (chipmjohnson)*


_Quote, originally posted by *chipmjohnson* »_I also recently had a CEL, which one coil pack was replaced. A few days later a second CEL and another bad coil. The Tech called VW and got authorization to replace the remaining 7 coils. 
Clearly there is an issue here. Hopefully they have done some type of redesign, so these issues won't continue.

Multiple simultaneous coil failures? They work for how many thousands of miles and more than one fails at the same time? Makes you wonder. I don't think we have any other reports of these failing on other Phaetons. I don't think the issue here is clear at all.


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## murphybaileysam (Dec 29, 2005)

*Re: Exhaust Warning Light (PanEuropean)*


_Quote, originally posted by *PanEuropean* »_You bought fuel in the Chicago area? That is the kiss of death for any W12 Phaeton (seriously). We have had all sorts of discussions in the past about the effects of the very high ethanol Chicago-area winter blend fuel on the W12 engines.
Michael

How can you tell what the winter blend of ethanol in the fuel is? Do you think it is different in say Indiana, Michigan or Wisconsin than Illinois? I have been driving my W12 for 2 winters now and have never noticed a fuel problem, (alright my CEL light has been on for months but I don't know what that's about yet).
I can fill up in any of the above mentioned states if the ethanol added is less but how to tell is the question.
Anyone else in Illinois experience fuel problems in their W12?


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## vah (Oct 12, 2007)

*Re: Exhaust Warning Light (murphybaileysam)*

no problem with fuel.


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## Motorista (Oct 28, 2005)

*Re: Exhaust Warning Light (car_guy)*

I agree with Steven: sounds very, very unlikely. I wonder if we could see a scan of the error codes that led tech to replace the coils?
Stefano
P.S.: the coils in my 17-yr old Acura Legend still work perfectly. I just checked with my Acura tech and he confirmed that they rarely, if ever, go bad.


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## Motorista (Oct 28, 2005)

*Re: Exhaust Warning Light (murphybaileysam)*

In some states, there's a sticker on the gas pumps. I recently filled up in West Virginia, for example, and noticed a label with an unusually high content (12% if memory serves) compared to what we have in Pennsylvania (105, I believe). In any case, it definitely varies from state to state.
Stefano


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## Green-T (Nov 5, 2006)

*Re: Exhaust Warning Light (Motorista)*

A few of the V8 Touareg owners have had to replace their coil packs due to the symptoms descibed here with the rough running engine and CEL. After repalcing coil packs problem solved.


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## JMMcMullin (Jan 20, 2006)

*Re: Exhaust Warning Light (mlong1)*

Marcos,
Steve Muholland and Mike have done a great job with my Phaeton since I bought it in Chicago 2 years ago. Several issues with the car but Mike uses this site for updates on issues. Steve told me about this site.
They'll do a great job while you own the car. 
Jeff


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## mlong1 (Dec 6, 2007)

*Re: Exhaust Warning Light (JMMcMullin)*

Jeff,
Thank you for sharing your good experience with Boardwalk. Those guys have had my car for the last 10 days. I hope all gets resolved correctly the first time.
BTW, I also bought my car in Chicago.
Marcos


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## seednik (Sep 6, 2007)

*Re: Exhaust Warning Light (mlong1)*

Just to follow up: today they diagnosed the problem as a bad coil. They are having it overnighted and will replace it in the morning. Thanks to all who provided similar experiences. It allowed me to steer the local VW service guys here in the right direction. 
Since there are only 2 Phaetons in town, they sometimes become easily confused


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## mlong1 (Dec 6, 2007)

*Re: Exhaust Warning Light (JMMcMullin)*

Jeff,
I got my car last night. Two coils were replaced. This morning on my way to the office the light came back!!!








One thing I noticed prior to the light turning on was a clumsy shift in gears at the first set of lights after leaving my house.
When your car had the engine light problem, could you feel any sort of clumsy gear shifting?
Marcos


_Modified by mlong1 at 6:41 PM 1-1-2008_


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## JMMcMullin (Jan 20, 2006)

*Re: Exhaust Warning Light (mlong1)*

No noticeable difference at any time when the light was on or off. Good Luck


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## seednik (Sep 6, 2007)

*Re: Exhaust Warning Light (JMMcMullin)*

Final note on my problem. As it turns out, the ignition coil replaced last week was not the problem. Went to another dealer who took a couple days of really going through the car carefully and found that one of the fuel injectors wasn't functioning properly. That was replaced and everything has worked properly since.


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## kgclark75 (Apr 14, 2006)

*Re: Exhaust Warning Light (seednik)*

My Exhaust System Malfunction light has just illuminated on my dash. I guess the conjecture that this error was somehow related to the cold can now be put to rest. (at least it's not in my case) I'm not experiencing any driving or transmission problems and really only drive at city speeds (and only maybe 30 miles/week). I'm at just under 50k miles and had the 50k service about 2k miles ago.
I'll probably be taking it in soon, but want to drive it for awhile to see if it goes away on its own before having to deal with my less than stellar service center again. If it is the fuel injector causing the problem (as indicated in a previous post), will holding off on a service visit cause any further damage?
Michael- This symbol is not listed in your "decoding symbols" linked post, but is identified in my user's manual.
Kevin


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## W126C (Jan 27, 2005)

*Re: Exhaust Warning Light (kgclark75)*

Hi Kevin,
I'm just curious here, did you put fuel with ethanol in you car? I get the check engine light every time I put ethanol in my W12. Also any fuel from the Chicago area. VAG-COM shows a " miss-fire " in one cylinder on the right bank and one on the left bank. Once cleared and back in Kansas, all remains good.








I just clear it out and caulk it up to weird fuel.
Regards,
Brent


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## stevieB (Jul 15, 2006)

when my exhaust workshop light came on in my diesel it cost nearly £1000 (pounds) to replace two parts one on the air intake and one on the exhaust, sorry i dont know what they were called , but the symptom was when sitting in traffic for more than 5 minutes a ton a white smaoke came from the exhaust when pulling away even at light throttle.


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## kgclark75 (Apr 14, 2006)

*Re: Exhaust Warning Light (W126C)*

Brent-
To tell you the truth, I'm not sure if Ethanol is in the gas here or not (Syracuse, NY). I do always use premium, if that makes any difference. 
Kevin

_Quote, originally posted by *W126C* »_Hi Kevin,
I'm just curious here, did you put fuel with ethanol in you car? I get the check engine light every time I put ethanol in my W12. Also any fuel from the Chicago area. VAG-COM shows a " miss-fire " in one cylinder on the right bank and one on the left bank. Once cleared and back in Kansas, all remains good.








I just clear it out and caulk it up to weird fuel.
Regards,
Brent


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## stevieB (Jul 15, 2006)

exhaust workshop light will come on if airfilter is blocked or dirty


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## W126C (Jan 27, 2005)

*Re: (stevieB)*


_Quote, originally posted by *stevieB* »_exhaust workshop light will come on if airfilter is blocked or dirty

I concur here sir. I was just curious about the ethanol. Most of the time it's the CAT fault code with the exhaust/CEL. I've had it a few times with the CEL. Which in turn is an air flow problem, not the CAT itself. I just am really hating ethanol lately.








Regards,
Brent


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## W12VW (Jun 24, 2005)

Here in south Florida, all of the gasoline sold now at the pumps is marked as containing up to 10% ethanol.
We have noticed a marked loss of miles per gallon in the Phaeton and in our R-R as well.
No warning lights etc.


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## kgclark75 (Apr 14, 2006)

*Re: (W12VW)*

Just an update - After about 2 weeks of driving, the warning light decided to reset to normal. Not sure what the problem was.....


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## KansasPhaeton (Mar 28, 2009)

*Re: Exhaust Warning Light (Frank N. Stein)*

Had w12 3days and at gas station after fueling exhaust warning light came on. Blinked a bit then stayed steady; car ran rough under acceleration/smooth crusing. Dealer said should go off in couple days, tow it in if it starts flashing. It's been a few days -it's still on; occassionally it flashes -just a little, then stays lit. Dealer is 100+ miles away. Not looking forward to whatever the process is here..
Question: Flashing is so serious stop the car and tow it? Or?


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## W126C (Jan 27, 2005)

*Re: Exhaust Warning Light (KansasPhaeton)*

Hi Duncan,
I'm going to be down in Wichita Saturday and returning to KC late afternoon. Maybe we can meet up somewhere and I'll VAG-COM your car for you. This way you should be able see what the problem is.
Let me know.
Regards,
Brent


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## KansasPhaeton (Mar 28, 2009)

*Re: Exhaust Warning Light (W126C)*

Thanx for your offer to assist; I am in Wichita (Friday 3/3 a.m.) and the w12 is in the shop (Steven VW) - I am waiting on their opinion. 
The warning light occassional flashes & the car than seems to run rough when flashing -top of hills and under acceleration. I've added 1/2 tank of gas -no difference.
I talked to Ross-Tech ---I'm assuming you've invested in the VAGCOM & Bentley Manual to at the least be able to see what's what --- I'm considering buying that stuff for that reason (& being 100 miles+ to the nearest dealer. )
I'd like as much input on the immediate problem as I can get and some schooling about general Phaeton ownership issues. There is a lot of technology to adapt to.. If you can email a phone #; I'll do same ; I'd like to talk to you.. Thanks again.


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## Kcmover (Jul 20, 2005)

*Re: Exhaust Warning Light (KansasPhaeton)*

Brent is your Jayhawk Phaeton expert!


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## W126C (Jan 27, 2005)

*Re: Exhaust Warning Light (Kcmover)*


_Quote, originally posted by *Kcmover* »_Brent is your Jayhawk Phaeton expert!









I have no affiliation with the University of Kansas or any other _round ball school._








Regards,
Brent


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