Author Topic: Exhaust/engine Warning Light on  (Read 5610 times)

Offline Greeners

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Re: Exhaust/engine Warning Light on
« Reply #15 on: January 31, 2009, 08:59:03 AM »
I hope you get it sorted today Illyun, our cars need to meet!  :evilgrin:

Offline Teutonic_Tamer

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Re: Exhaust/engine Warning Light on
« Reply #16 on: January 31, 2009, 09:42:31 AM »
Picked up my car from VWRacing today and drove down to Reading and then to Ipswich.  I was running low on fuel so very reluctantly stopped at South Mimms Services on the M25 - it was a BP garage and I didn't really want to put that fuel in the car... Anyway, I put in £10 of BP Ultimate (the bare minimum to get to Ipswich) and then drove off.. 5-10 miles later the exhaust warning light came on.  :sick:

This is most likely down to one of the following:

1.  Poor fuel from the BP garage destroyed the Lambda Sensor.

Whilst I personally don't 'rate' BP fuels, they are none-the-less good quality fuels - and I have never heard of any contamination issues or any other quality control issues.  That isn't to say that it can't happen - but South Mimms is a very busy service station - so stale fuel isn't going to be an issue - and I'm sure if there was a problem, many others would have had probs too.

2.  The Milltek exhaust that was installed about 1000 miles ago.

Who by?  Ask them what kind of exhaust sealants or hot bolt pastes were used upstream of the cats and lambdas.  If any non-approved compound is used, it can contaminate either the cat or lambda.  Most cats these days can tollerate tiny amounts of contaminents, but lambda sensors are very unforgiving.  Cast your mind back to the malicious fuel contamination of Tescos fuels a couple of years back - all affected cars needed lambdas renewing.

And with an aftermarket zorst (hopefully) being freer flowing - then the engine ECU may be 'surprised' by the sudden change in requirement for extra fuel, etc - and can throw some fault codes.  Reading further down the thread, I think you have found some fault codes to clear!  :wink:

3.  The APR Fuel Pump installed 3000 miles ago malfunctioning and sending too much fuel down - I did notice that my fuel range went from 50 miles to just 25 miles within 5 miles just before I stopped at the garage.

Even if the HPFP was overpressurising the fuel rail (yup, FSI engines also have "common rail"  :wink:), the actual quantity of fuel injected into the cylinders is determined by a two-way communication between each individual injector and the ECU - so this shouldn't cause the prob.  I could be wrong though!  :chicken:

4.  Exhaust Flapper Valve.

Nope.  Definately won't bring on the MIL.  I had one go on my last S4.  Started rattling, then seized in the closed position - and never lit the MIL.  Didn't even store a fault code!
Sean - Independant Automotive Engineering Technician (ret'd)
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Offline Teutonic_Tamer

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Re: Exhaust/engine Warning Light on
« Reply #17 on: January 31, 2009, 09:47:21 AM »
its down to the lower lambda probe getting lower temps so it sets it off

Why would it get lower temps?

Richer fuel mixture, retarded ignition timing, lower octane fuels.

Because of the S3 intercooler?  :confused: 

No - any change in charged air temps really shouldn't have any effect on EGT.  The inlet air temperature sensor will feed the relevent info to the engine ECU, and this should make adjustments accordingly.
Sean - Independant Automotive Engineering Technician (ret'd)
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Offline Teutonic_Tamer

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Re: Exhaust/engine Warning Light on
« Reply #18 on: January 31, 2009, 09:55:54 AM »
VAG-COM has found the following faults with the wheel speed sensor, DSG and fuel pressure  :scared:    Looks like I'll be visiting JKM at some point.  I'm not an expert  in diagnosing the readouts so I'll ask Northampton Motorsport what they think tomorrow.

VCDS Version: Release 805.2
Data version: 20090111

<snippage>

A longlist of what seem to be unrelated fault codes is often a result of low battery voltage.  Have you had any battery issues?  Do you have a multimeter?  If so, check the voltage across the terminals (with the engine, ignition, and interior lights all OFF), and as a bare minimum, it should be 12.7 volts, and have an 'ideal' volts of 13.2 volts.  Then start it up and after half a minute or so, check again, and the alternator should be charging at around 13.8 volts, with a maximum of 14.7 volts from an alternator.

And did you actually clear all the fault codes?  :confused:
Sean - Independant Automotive Engineering Technician (ret'd)
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Offline Teutonic_Tamer

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Re: Exhaust/engine Warning Light on
« Reply #19 on: January 31, 2009, 10:12:19 AM »
The wheel speed sensor fault may be due to something VWR did when putting the Quaife on..

But the two rears are affected too!  :wink:  And all four wheel speed sensors have the identical fault - any chance of that happening with 4 actual idential faults, all at the same time - is as rare as rocking horse manure!  :wink:

but then again all the faults occured at the exact same time because the mileage is the same on all fault freeze frames - or am I not understanding them correctly?

You have understood correctly (all the faults at an identical time).  As touched on earlier, because so many faults, in so many different modules have fault codes - then this is a very classic case of low battery voltage.  One of the codes does specifically mention low voltage!  :wink:

Looking again, it does appear as though your alternator is charging fine at tick-over.  If you get chance, raise the engine revs to a steady 2,000 rpm, and check the voltage across the battery terminals - just to rule out any over-charging issues which might be frying your battery.


Finally, why did the exhaust/engine light come on approximately 257km/160 miles later instead of at the time of the fault?  I thought these things are real time aren't they?

Fault codes are generally stored in 'real time', but the warning light doesn't have to come on when an engine (or engine related) fault code is stored.  Usually, the engine warning light only illuminates permanently if the ECU senses so many faults, or 'accumulated' faults over a period of time, or where an individual fault means the ECU can not adjust for (such as a toasted ignition coil, a slipped timing belt, etc) - and when the light does come on, it usually reverts the car to "Limp Home Mode".  Now, how limp home mode works with a remap - I havn't got the foggiest!  :confused:

But can you clarify - did the warning light come and stay on, or did it flash on and off intermittantly?
Sean - Independant Automotive Engineering Technician (ret'd)
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Offline Teutonic_Tamer

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Re: Exhaust/engine Warning Light on
« Reply #20 on: January 31, 2009, 10:17:41 AM »
Those are some codes I would expect to see from a car having been on a Dyno.

Agreed, though invariably, the type of fault codes generated by an RR (two wheel only - 4-wheel RRs don't have this issue) are generally not 'importatant enough' to affect the subsequent engine operation.  Again, could be wrong though!

Clear them off and go for a drive, see what happens and let us know.

Spot on.  Best piece of advice in this thread!  :happy2:

It is well known and accepted that REVO reverts to 000 when the battery is removed.

Didn't know that - thanks for sharing.  :happy2:

So if you don't have the revo select switch, do you then have to have it reflashed by the revo agent?  :confused:
Sean - Independant Automotive Engineering Technician (ret'd)
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Offline 182_blue

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Re: Exhaust/engine Warning Light on
« Reply #21 on: January 31, 2009, 10:20:41 AM »
i removed your VIN number from the thread  :happy2: