# Emissions Warning Light On



## melltt (Oct 5, 2006)

The emissions warning light came on today and has stayed on. Vehicle running OK. At first I thought it was a gearbox/transmission fault as the symbol looks more like that.
Handbook says take to dealer right away. Booked in for wednesday (first chance for a courtesy car) but dealer said OK to drive if no fault apparent.

Wondered if anybody else had any experience with this fault light coming on ?


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## andya (Jun 17, 2003)

Yup, on both a TT and a Golf.

could be things like coil pack failure, lambda sensor failure etc. car might appear to be running normally but you could be damaging your cat by dumping unburnt fuel in it... worth getting Audi Assist out asap to diagnose and/or dealer.


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## Toshiba (Jul 8, 2004)

Had it on the V6 a few times, just cleared itself after been sat for about an hour.


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## muf722 (May 20, 2008)

It may be caused by overfilling the tank. Fuel will get to the lambda probe and turn on the light. I had the problem on a VW car and now I never overfill again.


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## andya (Jun 17, 2003)

muf722 said:


> It may be caused by overfilling the tank. Fuel will get to the lambda probe and turn on the light. I had the problem on a VW car and now I never overfill again.


Eh! The probe is in the exhaust system...how does overfilling a tank cause fuel to get into the exhaust system?


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## melltt (Oct 5, 2006)

Toshiba said:


> Had it on the V6 a few times, just cleared itself after been sat for about an hour.


Nope. Still there after 20 hours.


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## ricka (Mar 31, 2007)

I had it on a MK5 Golf - it was a dealer job to turn it off, straight forawrd enough though.
They said there was nothing wrong e.g. drive it etc but it was just a faulty warning indicator :? 
They also said that it's only something to worry about if the warning light begins to flash.
No disrespect to anyone but I had no end of problems with both MK5 Golfs I owned. Hope the MK6 is better! 
I've had none of the issues with Audi that I had with VW.


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## Toshiba (Jul 8, 2004)

ricka said:


> I Hope the MK6 is better!
> I've had none of the issues with Audi that I had with VW.


MK6 is the same car - just made cheaper.


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## melltt (Oct 5, 2006)

Been told today that the lambda probe needs replacing. On delivery overnight and fitted in the morning.

For those like me who didn't know exactly what this did I've piched the following from the net. The interesting thing is in the last paragraph regarding lifetime, which should just take it out of warranty normally

*Lambda probe*

An automotive oxygen sensor, also known as an O2 sensor, lambda probe, lambda sensor, lambda sond or EGO (exhaust gas oxygen) sensor, is a small sensor inserted into the exhaust system of a petrol engine to measure the volume of oxygen (O2) remaining in the exhaust gas to allow an electronic system (ECU) to control the efficiency of the combustion process in the engine. In most modern automobiles, these sensors are attached to the engine's exhaust manifold to determine whether the mixture of air and gasoline going into the engine is rich (too much fuel) or lean (too little fuel). 
This information is sent to the engine management ECU (electronic control unit) computer, which adjusts the mixture to give the engine the best possible fuel economy and lowest possible exhaust emissions. Failure of these sensors, either through normal ageing or the use of leaded fuels, can lead to damage of an automobile's catalytic converter and expensive repairs.

*Function of a lambda probe *

Lambda probes are used to reduce vehicle emissions, by ensuring that engines burn their fuel efficiently and cleanly. Robert Bosch GmbH introduced the first automotive lambda probe in 1976. The sensors were introduced in the US from about 1980, and were required on all models of cars in many countries in Europe in 1993. [/color]
By measuring the amount of oxygen in the remaining exhaust gases, and by knowing the volume and temperature of the air entering the cylinders amongst other things, an ECU can use look-up tables to determine the amount of fuel required to burn at the stoichiometric point (14.6:1 air:fuel by mass) to ensure complete combustion.

*Location of the probe in a system*

The probe is typically screwed into a tapped hole in the exhaust, located after the branch manifold of the exhaust system combines, and before the CAT (catalytic converter).

*Common failure modes *

Lambda probes have a limited lifespan since the exposed sensor element is subjected to high temperatures which causes fatigue over time. Probes become sluggish, failing to react quickly to changes in the condition of the exhaust gases. This can be caused by contamination from the engine, fuel or additives. One common fault is silicon buildup on the probe sensor. A common source of silicon contamination is through the use of silicone sealant in repairing water system leaks. Lead build-up from the use of lead additives or leaded petrol will also damage the probe, as will carbon build-up from excessive burning of engine oil. Phosphorus in the burnt oil is also a specific damaging contaminant (but the phosphorus is part of a very beneficial additive called ZDDP which as of 2005 is yet to be replaced with a less 'damaging' (to the sensor or emissions equipment) yet equally effective (in protecting the motor life) substitute. It would be expected that a probe would last for 3 years or 40,000 miles (about 64,000 km), but it has been observed that probes will last for up to 3 times this length. [Also, oxygen sensors have been used successfully for 2 years of racing with leaded gas when the sensor is put into a non-leaded gas burning vehicle to 'burn' off the lead then putting it back, etc.


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## Marcr (Jun 20, 2009)

wonder if that could be my problem... engine running very rich and turbo is not boosting properly at high revs?


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## heatserve (Jul 12, 2009)

hi, picked up 2007 3.2 TT from garage, drove fine for 30 miles, when stopped and restarted car, ECS light started to flash, car run erratic, then light stayed on , managed to drive home on low revs. Manual says, poss CAT or Fuel. any ideas. Phil


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## andya (Jun 17, 2003)

heatserve said:


> hi, picked up 2007 3.2 TT from garage, drove fine for 30 miles, when stopped and restarted car, ECS light started to flash, car run erratic, then light stayed on , managed to drive home on low revs. Manual says, poss CAT or Fuel. any ideas. Phil


Could be coil pack failure and misfire. If it's running rough due to a misfire it's not so distinctive as with the 4 cyclinder engine as you've only lost 1/6th rather than 1/4


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## BLinky (Jul 3, 2009)

if its an ignition coil then it's very easy to replace asuming you can figure out which one it is, just disconnect the leads and pull them out and see which ones make a difference which doesnt etc etc use an educated guess they cost 25 - 50 quid from the parts department at an audi dealer and all that needs doing is pulling the burnt one out and putting a new one back in, the light may stay on for a day or so and it will disappear asuming you changed the right one(s), you'll know if you changed the right ones by listening / driving the car if the car drives fine and is smooth then you know you've done it right. its common for pairs to go at the same them, just pull them out(with a little force) and see which one looks funny, burnt... moisture etc etc 5 min job. no need for 40quid diagnostic or leaving it at a dealer.


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## heatserve (Jul 12, 2009)

andya said:


> heatserve said:
> 
> 
> > hi, picked up 2007 3.2 TT from garage, drove fine for 30 miles, when stopped and restarted car, ECS light started to flash, car run erratic, then light stayed on , managed to drive home on low revs. Manual says, poss CAT or Fuel. any ideas. Phil
> ...


Thanks for your advise, you were both correct, it did turn out to be coil failure, didnt expect any breakdowns in the first 30 miles of me owning a new 20k car supplied by main dealer thou. thanks once again


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