Emissions Light

[charlton_68]

Having searched the forums i've not got the exact answer I'm looking for.

The 182 i've just bought previously had a decat fitted with Milltek exhaust system, triggering the Emissions Light on dash as per usual. The previous owner said the decat was a little loud, so he got rid and put a cat back on, however the Emissions Light stayed on.

When I bought the car I took it to my local garage who has one of those code readers and he cleared the code for me for free and the light disappeared.

I drove the car on 2 short journeys (5miles each). Then on my 3rd journey the Emissions Lights came back on (had covered about 20 miles in total).


Now I know most people will just say, just put up with it etc, but its bloody annoying!! The car drives fine, I think?? Only saying this as I know no different, but it does seem to drive spot on still.

 

[Reecey]

its all good clearing codes, but with emisions they will come back on because the ecu will read the next lot of emisions that will pass through the exhaust and again realise the problem...try changing the lamda sensor. That could be the problem.

 

[LowLife.]

Lambda sensor would more than likely be the problem. You could try swapping the two over?

Might save you buying a new one?

 

[charlton_68]

Cheers lads, I have read it could be the lambda sensor. Out of interest what would swapping the 2 sensors around do? (Genuine question, sorry I don't know much about engines etc).

Also interested as to what the actual problem with the lambda sensor is? Just wear and tear? Or does a decat destroy them?

 

[LowLife.]

I believe its the upstream sensor (the one nearest the engine) displays the light.

So if you swapped the sensors over, then cleared the fault code, it should keep the light off.

As I believe the second sensor doesn't display the light? This is how I believe it would work?

 

[charlton_68]

I believe its the upstream sensor (the one nearest the engine) displays the light.

So if you swapped the sensors over, then cleared the fault code, it should keep the light off.

As I believe the second sensor doesn't display the light? This is how I believe it would work?

Ahh ok, isnt the downstream responsible for fueling though?

Meaning if there was infact a fault with the upstream sensor, the car would then over fuel? Or am I wrong? :lol:

 

[LowLife.]

I am not too sure mate.

I swapped mine over a few months back to get rid of the light. But replaced both since then lol.

Best bet is to try a new upstream sensor.

 

[Poopensharten]

From memory, the downstream is the business end sensor.

GSF sell OEM bosch items for £66 inc. vat.

 

[LowLife.]

Don't get an NGK one whatever you do lol.

Nuff said.

 

[Tigger]

Mine has randomly came on on the motorway. Have stopped a few times with engine off but light stays on even before I turn over at startup. Car drives fine too.

This happened me before one night and went away again :S what causes it anyone know?

 

[TrackdayAl]

No point just clearing the code and guessing what to change.

Read the codes and actually look at what it is pointing towards.
Remember a code read is only a pointer and not the actual sensor at fault.

 

[Tigger]

Fault code P0420 came up on mine - cleared it and it's been fine, went for the exact same drive as I did yesterday after topping up with super unleaded (that's when it came on)

 

[Aaron182]

Seems to be a intetmittent fault mine has had two new lambdas and the light still comes on once a month even with std exhaust and cat.
When i fat my exhaust and decat i couldnt get the lambda out the cat so drove it home without it light diddnt even come on decat diddnt make a difference.
You will have to live with it lol

 

[TrackdayAl]

Fault code P0420 came up on mine - cleared it and it's been fine, went for the exact same drive as I did yesterday after topping up with super unleaded (that's when it came on)

Have you got a decat? If yes and both o2 sensors are still fitted then it is understandable.

If you havent got a decat then might be worth looking at getting one as normally this means cat is screwed. If you go into live data with a scantool and monitor both the oxygen sensors it will confirm this.

http://www.ukdiagnosticdirectory.com/obd-codes.html

 

[Tigger]

I ran the car for a good half-hour on a mates fault reader. Also records graphs of all the sensors - selected the 2 oxygen sensors and drove it as said. All is well so far

PS - I have the K-Tec sport cat & supersport recessed system rrrrRARRRR!

 

[TrackdayAl]

I ran the car for a good half-hour on a mates fault reader. Also records graphs of all the sensors - selected the 2 oxygen sensors and drove it as said. All is well so far

PS - I have the K-Tec sport cat & supersport recessed system rrrrRARRRR!

Ok both sensors would have been switching, from 100mv to 900mv then this is why the P0420 was flagged. The 2nd o2 sensor is only fitted to monitor efficiency of the cat.

Moral of the story, if that code comes back dont change the o2 sensor as it wont change bugger all.

I have a Renault Clip :rasp: (or five)

 

[Tigger]

Aye it came on before on the way home from Belfast one night - but when I got into the car the next morning it was fine until yesterday