Engine Mangement Light

23rd November 2010, 18:05

Hey, does anybody know anything about the Yellow engine management light for a 2002 VTR. The light came on a couple of weeks ago and I took it to the gararge for a check. They managed to turn the light out suggesting that the error code stated the CAT was worn. I was a little supprised as I had a new cat fitted 12 months ago. Unfortunately after a week of no engine management light it has returned????

23rd November 2010, 18:13

Lambda sensor..

23rd November 2010, 20:34

Kwl thanks for that. Apparently there are two of them front and rear (what the garage said). Do I need to replace both of them?

23rd November 2010, 20:48

The first one (green plug if memory serves) goes before the cat, measures the emissions straight from the engine.

The second one (blue plug.. maybe) goes after the cat and measures the emissions to test whether the cat is working or not.

If the first sensor wasnt working then as far as I know, the engine wouldnt run correctly.
The second one is only a warning to let you know the cat isnt working. It'll make no difference to the running of the engine if this sensor is faulty.

23rd November 2010, 21:16

Cheers for that. Blue and Green was kinda mentioned by the assistant at Andrew Page today re sensors. The engine is running fine so prob go for changing the latter one 1st and take it from there. P.S anyone know how to reset the light or will this go off automatically once the sensor has been replaced. Bloomin £50 notes to have it reset for all of 5 days last time lol ... They saw us comming !

23rd November 2010, 21:20

Yes - unplug the battery for half an hour - don't pay 50 notes for a reset!

23rd November 2010, 21:33

Thanks again, Yeah will def give that a try. Cats & Sensors eh??

23rd November 2010, 21:45

French and Saxos!

23rd November 2010, 22:01

Hey thats why the French are so miserable.

23rd November 2010, 22:02

I don't know how good you are with electronics but it's quite easy to test a lambda sensor.

If you attach a multimeter to the lambda (while it is connected to the car and with it running) then you should see it alternating between 0.2 and 0.8 volts in a wave pattern.

Connect the red test lead of the meter to Black (or Purple)
Connect the black test lead of the meter to Grey (or Beige)
Ignore the two white or brown wires, these are for cold start heaters.

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^^
Thats the kind of thing you should see if it has got a bar readout, otherwise just look for 0.2~ to 0.8~ back to 0.2~

24th November 2010, 10:48

Whats a Multimeter lol? Only joking. Thanks for that, will deff give it at try. From what I have read so far it sounds like it is more likely to be the 2nd sensor that maybe at fault as the car is running fine. Checked the Haynes manual and from the wiring diagrams it only suggests a single O2 sensor. Was thinking about removing a fuse (F11) but I guess that will make the car run like crap lol? Thanks again for the tip, typically the 2nd sensor is under the car me thinks.

24th November 2010, 10:52

so what happens if its the front one that shows up a problem does that mena its the engine? or the sensor? or even worse both?

24th November 2010, 12:01

mines appears now and then its been checked its fine faulty sensor as others have said this si what happend when we buy french shite

24th November 2010, 13:16

Hi, re the front sensor thing (#12). I did have the error codes read buy the garage (got to get something out of my £50) The error codes read faulty/worn cat. As the cat is about 12months old, this is why we think it is the sensor. I will post the codes on when I find the paper with em written on. Suppose its a bit of a guessing game if you have not had the error code read, to if its the sensor or another worse problem. Just hope that its the sensor at fault. Will let you know.

24th November 2010, 13:36

I think? again not too sure if this is too exact. But the 1st sensor is connected to ECU and from information it receives the ECU responds acordingly, varying the time the injectors are held open to provide a weaker or richer mixture. Thus if the sensor is out the car will run rubbish. 2nd Sensor? No idea what that one does? But seems to be on multi-point injection cars only? Again maybe wrong so feel free to correct us if so.

24th November 2010, 14:32

My Mk.1 Saxo only has a pre-cat sensor in the manifold, the post cat (2nd) in cars that have them reads the O2 in your nice 'clean' air to make sure your emissions are with in tolerances - if not - then EML will come on, but generally the lambda's seem to fail before that cat's do

25th November 2010, 11:09

From what I read in the good ol Haynes, Cats can last anything from 50k to 100k if looked after. Wish the Mk2 only had one O2 sensor. All these emissions test are a pain. Say, if you get a De Cat pipe you will pretty much have to live the EML on all the time??

25th November 2010, 14:14

From my understanding; when the engine is idleing, or under steady load the ECU will work on closed-loop which will take the readings of the sensors to change from slightly lean to rich and back again. Too much time like this with a post cat sensor on a de-cat pipe will probably put the EML on because the expected readings won't match. In normal driving, the ECU changes to open-loop which means the fueling operates from a stored map, le citroen disregards European emissions, and it works as it should.. for a while

Thats why you can get a way with a week or so with no EML with a knackered sensor

30th November 2010, 20:50

Funny enough that could explain why the EML light on ours came on at pretty much the exact same place both times. Queing at some temp traffic lights for about 5 or 10 mins.

Still not had time to fix the thing yet. My boss is to blame, sending us to Birmingham for the weekend. Now Snow.....

29th January 2012, 15:10

BTW.... The EML went out on its own the other week after being on for 14ths. Even though I bourght a new sensor, I never changed it coz the existing one was so happy where it was, it didnt want to budge.... Not complaining!