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Author Topic: Mysterious check engine lights  (Read 322 times)

Offline OllieVRS

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Mysterious check engine lights
« on: January 11, 2022, 05:20:27 pm »
600 miles ago got a CEL waiting at a red light caused by the diverter valve, error: 'N249 Mechanical Malfunction'. My friend cleared it for me and it didn't come back since.

Now I got another CEL while also at a red ligt, and I scanned it with my cheap OBD scanner.



There was no change in performance or engine sound.

I cleared it and drove to work without the light coming back, nor any drop in performance.

Any ideas what it could be guys?  :smiley:

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Re: Mysterious check engine lights
« Reply #1 on: January 11, 2022, 08:44:56 pm »
I lived with that fault for a while, you clear it, it stays away for weeks and then comes back - no real noticeable change in running.

It is either or both:
The carbon canister - it brakes down internally with debris going into the valve - ebay or amazon chinese ones less than £20
The N80 evap control valve - stopped working or blocked - OEM is made by Bosch and are over £70, but last time I checked genuine Bosch aftermarket ones £30 to £40 on ebay.

I hope the Octavia is otherwise behaving itself?




Offline OllieVRS

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Re: Mysterious check engine lights
« Reply #2 on: January 12, 2022, 10:37:02 am »
I lived with that fault for a while, you clear it, it stays away for weeks and then comes back - no real noticeable change in running.

It is either or both:
The carbon canister - it brakes down internally with debris going into the valve - ebay or amazon chinese ones less than £20
The N80 evap control valve - stopped working or blocked - OEM is made by Bosch and are over £70, but last time I checked genuine Bosch aftermarket ones £30 to £40 on ebay.

I hope the Octavia is otherwise behaving itself?

Thanks for the reply LC5F!

She sure is, other than the random ticking of the tfsi engine  :wink:. It just always gives me a heart attack when something pops up on the dash in this car, paranoid that I'm gonna have to spend €€€€ fixing it again.

It's so strange though that the first time it was the diverter valve throwing an error, and now this 600 miles later. I guess it's a typical VW after all  :grin:

Offline Pudding

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Re: Mysterious check engine lights
« Reply #3 on: January 12, 2022, 10:54:08 am »
A bad seal on the petrol cap can also cause evap fault codes as well, believe it or not.   It's a very tightly controlled and monitored closed loop system, because......effin Brussels.

You might want to get onto that sooner rather than later as you don't get any fuel trims/adaptations whilst the evap circuit is flagged as faulty.

Indeed VWs of this vintage are moody, inconsistent, money draining, ungrateful wenches.

I walked past an EP3 Civic Type R the other day and had rude thoughts.  Buy one for a couple of grand, have fun with it for a while (not stressing about oil pressure, carbon build up, failing injectors, worn out HPFP followers etc etc) and then turbo it  :laugh:



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Offline OllieVRS

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Re: Mysterious check engine lights
« Reply #4 on: January 12, 2022, 11:26:52 am »
Cheers pudding, I sometimes too have doubts about whether to keep my VRS but then I remember that mk5 gtis cost ~€7000 and civics ~€9000 and both are uninsurable for me  :grin: nor are there any other petrol VRSs on the Irish used car market atm.

I've driven about 20 miles since clearing the code and it hasn't come back, should I wait until the code comes back again or is time to start throwing money at it again?

The petrol cap is a big wiggly when screw on, but I have nothing the reference off of. I did read that brimming the tank could also throw a P0441, which is what I did do a few days ago.

Offline ttelracs

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Re: Mysterious check engine lights
« Reply #5 on: January 12, 2022, 12:23:57 pm »
I had a similar issue with my previous steed, a BMW E39 530i Sport and I spent age phaffing in the engine bay changing hoses and ensuring tight fits then read about the fuel cap.  Instead of replacing I removed the rubber seals, put them in hot water for 5 mins and then replaced with some silicone spray which worked (well for about 500 miles).  After I bought a new cap on eBay and problem solved.

As @Pudding mentioned a slight inconsistency on the sealing of the cap can throw all manner of dodgy codes, very similar to a failing battery which still starts, runs the car with no visible issues and showing a good voltage BUT is still on it's way out.  Good luck.

Offline Pudding

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Re: Mysterious check engine lights
« Reply #6 on: January 12, 2022, 01:52:02 pm »
Hmmmm, you're right.  Just looked on Autotrader and EP3 Type Rs are £3,500 minimum, so sod that as a cheap run around idea then  :grin:  5-6 years ago, you could pick them up for £1.5-£2K.  Madness.

Yeah leave it until it moans again before cracking open your already battered to death wallet.

I've heard that about brimming the tank but it's never happened on mine, and I do literally click the pump 5 or 6 more times after the first!

Check the cap seal for any obvious signs of damage but usually they look fine.  When I got the evap fault code years ago, I replaced the N80 solenoid - no change.  Changed the petrol cap - no change.  Changed the carbon can - sorted.

The problem with that fault code is it's not specific enough. The ECU just reports "incorrect flow".  Well that could be from a solenoid stuck shut (or open), depleted charcoal in the carbon can, leaking petrol cap etc etc.

Bloody cars  :grin:

Yeah that's a good point re the battery.  They can and do die slowly, but not to the point of causing problems, apart from maybe slower than usual electric windows, slightly heavier steering than usual, etc.  Thankfully I bought a lifetime warranty battery from Halfords  :smiley:


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Offline OllieVRS

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Re: Mysterious check engine lights
« Reply #7 on: January 12, 2022, 01:55:44 pm »
Just ordered a Febi Bilstein 27288 fuel cap as it's only €8 off of Amazon UK. If it doesn't fix the issue I'll get the €20 Bosch N80 Valve off Amazon too. Hopefully I'm not starting another money pit here  :grin:

Offline Pudding

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Re: Mysterious check engine lights
« Reply #8 on: January 12, 2022, 03:09:20 pm »
Shouldn't be another pit!  At least with this problem you don't have to climb under the car and get covered in oil  :grin:


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Re: Mysterious check engine lights
« Reply #9 on: January 12, 2022, 09:46:48 pm »
She sure is, other than the random ticking of the tfsi engine  :wink:. It just always gives me a heart attack when something pops up on the dash in this car, paranoid that I'm gonna have to spend €€€€ fixing it again.

Glad to hear it - they all tick! - Get valium

Offline OllieVRS

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Re: Mysterious check engine lights
« Reply #10 on: January 15, 2022, 11:33:35 pm »
I drove about 100km before I put on the new fuel filler cap on earlier today. No lights so far.

Feels similarly wiggly to the old one so dunno if it made any difference.

Also did a longer, spirited drive after putting the new one on. Happy to report no lights, just loads of fun driving instead (and losing a rolling race to my friend in his 2015 GTD DSG :sad1:  :grin:).

A few ponies must have darted over the years methinks, or the octane booster isn't doing it's job.
« Last Edit: January 15, 2022, 11:35:09 pm by OllieVRS »

Offline Pudding

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Re: Mysterious check engine lights
« Reply #11 on: January 19, 2022, 12:14:57 pm »
MK7 GTDs are deceiving!  They don't feel fast at all to drive (MK6 GTD feels quicker), but come up against one that's game for a race in your GTI, they can take a lot of work to overtake!

If you'd said you'd lost a rolling race to a Prius, then fair enough, your car has problems.  But a GTD isn't anything to be ashamed of, especially a DSG one, with only a 20hp deficit on yours.....but considerably more torque!

I'm actually considering binning off my ED30 to get a MK6 GTD as it happens.


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