Emissions Light!

[Jollus]

Im sure I have seen my emissions light come on more often than i switch my dashboard lights on aye! What a nuisance its becoming. It was a few months ago it started for lambda sensor post cat so changed it, all went well for a month or two untill the light came on again, this time for brake light switch. Changed that reset the light and went well for months untill the light came on for pre lambda so have changed the pre lambda too which was over a £100! Now the light has come back on again for pre lambda when theres two genuine vw new ones on there! Can anyone shed any light as to why it could be coming on? I have reset the light which has stayed off for a while now.

I had a bit of an emissions nightmare trying to get the car through MOT. It was found to be a leakly sleeve on the exhaust which i tapped back in and placed a new clamp on it, it then passed the MOT. Could this problem with the exhaust be back and causing the light to come on cos the readings too high or low?

Many thanks

[RUM4MO]

Which engine do you have? I've had the pre cat probe fail once only - and yes £100+ is a bit steep, its as cheap from VAG as a genuine NTK (NGK) one is from elsewhere including p&p. One horror story about getting a repeat failure of these probes is contamination by silicon that might come from a failed cylinder head gasket - that was reported once! I was going to ask you to explain about the leaky sleeve as I thought you might be meaning the flexi section of exhaust, but I've realised that you probably meant the middle joining sleeve. MOT places don't seem to worry too much about that and it should not have caused any other problems. If your engine has an EGR system, have you checked the operation of this - or checked that it is clean? What was your first and second pre cat probe codes - mine was just S1 output and S1 heater problem.

[Jollus]

Thanks for your reply, I have a 1.4 16v Petrol engine. Yeah pre cat probes are a pain but its strange how the fault has come up as pre cat probe again after replacing with brand new NTK. Sorry I cant explain much more about the leaky exhaust it was just a thought. I dont know which section was leaking i think it was the sleeve near to the backbox but nearly in the center of the car. Im not sure if I have an EGR system whats that? Im not sure of the outcome codes just that it was associated with pre cat probe again. I cant think why else the light would be coming on. Its stayed off now for a few weeks so fingers crossed lol.

Thanks

[chewy]

Could be the brake light switch behind the brake peddle

[RUM4MO]

Could be the brake light switch behind the brake peddle

Yes but he has already had, and recognised that problem I think!

[RUM4MO]

Thanks for your reply, I have a 1.4 16v Petrol engine. Yeah pre cat probes are a pain but its strange how the fault has come up as pre cat probe again after replacing with brand new NTK. Sorry I cant explain much more about the leaky exhaust it was just a thought. I dont know which section was leaking i think it was the sleeve near to the backbox but nearly in the center of the car. Im not sure if I have an EGR system whats that? Im not sure of the outcome codes just that it was associated with pre cat probe again. I cant think why else the light would be coming on. Its stayed off now for a few weeks so fingers crossed lol. Thanks

Right joining sleeve near the middle of car - that is what I thought you meant, but that is post cats so should not affect the emissions system. How are you getting the fault codes read? You will have an Exhaust Gas Recirculating system with that engine. Exact fault code numbers and description might help a bit - save guessing (hopefully).

[chewy]

Could be the brake light switch behind the brake peddle

Yes but he has already had, and recognised that problem I think!

Yeah must remember to read the message fully before I reply

[vwpolo16v]

I've had my Emissions light ON for nearly nine months
...and the car seems to run fine (touch wood).
That is, runs smoothly, no hesitations or jerk and no loss of power since got the car.
OK well it could do with a bit more poke but then don't we all have that wish

The VAG COM shows the following fault codes (which I don't really understand):
16786 - EGR System: Excessive Flow
P0402 -- 35-00 - -
Readiness: 0000 0000

I can turn off the emissions light but of course comes back on within 10 miles of driving.

So...the question I have is what's this brake pedal switch got to do with emissions ?
if the car running fine, could this switch thing be my problem ? If so is it easy to checkout ?

[chewy]

I took mine into vw because the engine light and epc light were both on turned out to be the brake light switch under the pedal. Next day the engine management light came back on and this time it was the egr valve.

[RUM4MO]

Could be the brake light switch behind the brake peddle

Yes but he has already had, and recognised that problem I think!

Yeah must remember to read the message fully before I reply

Ditto for me!!

[RUM4MO]

I've had my Emissions light ON for nearly nine months
...and the car seems to run fine (touch wood).
That is, runs smoothly, no hesitations or jerk and no loss of power since got the car.
OK well it could do with a bit more poke but then don't we all have that wish

The VAG COM shows the following fault codes (which I don't really understand):
16786 - EGR System: Excessive Flow
P0402 -- 35-00 - -
Readiness: 0000 0000

I can turn off the emissions light but of course comes back on within 10 miles of driving.

So...the question I have is what's this brake pedal switch got to do with emissions ?
if the car running fine, could this switch thing be my problem ? If so is it easy to checkout ?

You should take a look at http://wiki.ross-tech.com and look for that fault code for clues.

[Veedub9n]

When my emissions light came on it was becasue of a broken lambda sensor. The MPG went down a lot aswel. Had an emisisons test on it and it was running 10x times than what it should have been. Easy to fit just a bit of money for a small part.

[Jollus]

Thanks for your help guys im goona have a browse for these fault codes online. Yeah I had the brake light switch problem before and replaced it and havent seen that code since. Unbelieavably after two weeks of running fine, the light came on today. The RAC read the fault code out as both lambda's! Pre and post cat lambdas with the info of "Control limit reached" the numbers of these two faults were: -
P0140 16524
P1176 17584
Any help on what to do next would be greatly appreciated. I have only recently changed both these lambda's with genuine VW ones. ARgh! lol

Thanks again

[RUM4MO]

Jollus,I'm not completely clear why the RAC guy thought that both Lambda probes were dead, the first code relates to "no activity " bank 1 S2 - that means the post cat monitor probe, the second code claims " after cat control limit reached" - the first probe, ie bank 1 S1 is the control probe - normally any faults with that would show up as bank 1 S1 logged faults. Really this is just guess work but you could have a duff or dead cat - if you have one of these cheap Maplin IR thermometers then you could check the exhaust temperature to see it its hotter after the second cat than before it. Remember that these lambda probes cost roughly £130 for the first one and a bit less for the second one - so guessing can get expensive, although if the cat is dead, then it would be smart to replace the probes as well. Continuing down the guessing path (not very smart I know), I'd think that replacing the post cat probe - ie bank 1 S2 would be your first shot in the dark - as "no activity" is not much good and that would leave the emissions system confused as it would not be seeing any change after altering the fuelling.

Hum, I've realised that you have changed both these probes already - this should not be happening so soon, so there could be another problem, when you replaced the S2 probe, you did not notice any damaged wiring where the plug/socket join? This plug/socket must still be connected as you are not getting a warnings about heater circuit failure (I'm guessing that the S2 probe is heated).

[Jollus]

Well the Rac man seemed to think there was a problem with the both of them as it threw two codes at the same time related to both the sensors. Its really strange how the new genuine ones havent stopped this light coming on. Yes I think I may get the cat checked out somehow in order to see whats wrong with it. I believe that the wiring is OK. I didnt fit the probes myself but the guys who did the work didnt report any problems with the wiring. Well I will get my cat checked out and report back ;-D

Thanks man