Hi guys, my 1998 cabrio 1.2 16v failed mot earlier this week on emissions. Usual suspect is the lambda, so I replaced it today.

To double check if the lambda is ok, I read out the ECU and found two errors codes, electronic key and the lambda sensor.

As a Mac user, I had to use my old xp laptop, with very limited battery life, so after I had Multiecuscan working I didn't have much time left to try several things.

The strange thing is that Multiecuscan gives an error code, but in the parametres overview the status is closed loop, meaning the sensor is working, is this correct?

What am I missing here? Or what kind of extra test should I do with Multiscan?

I believe when the lamda goes the ecu does not know it and tries to use it. But the lamda sensor shows a reading when CO is present in the exhaust. When it dies it stop showing a reading when CO is in the exhaust and the ecu thinks that the engine is running lean. To compensate for this, the ecu makes the mixture richer to see if the lamda sensor reacts. If the lamda is partly bad the ecu will still use close loop to try to adjust the mixture and if this works then the CO will be high despite the ecu thinking is doing the job right. I think the ecu on our cars is pretty primitive and is not able to detect a bad sensor, so the best bet is to just replace the lamda and see if problem is fixed. I use a conventional old school CO meter and when my lamda dies the CO reading shows 10%. A lamda swap causes the reading to go to 0%. When my lamda is bad the ecu does not show any warning lights (1.2 8V engine though), so I suspect it still tries to use the lamda in close loop mode, even when the lamda does not output any voltage.

Thx dumbledore for your extensive answer. I have replaced my lamdba before I did the test, so the lambda it self shouldn't be it.

What's left faulty wiring, reset ECU?

If you replaced lamda and is not working correctly, I would just double check the wiring. Did you use original with wiring loom? Or did you use generic. If generic yes, recheck wiring.

I got this one should be plug and play. http://www.bestpartstore.co.uk/7081519That doesn't mean there can't be anything wrong with the wiring ofcourse, but how can I check this?

Looks like you got genuine one and wiring should be fine.
You need now to check how bad the emissions are with the new lamda.
If CO is marginal fail, then the lamda is OK, but something else needs attention. Is the engine running good?

I suspect that is a stored code and not live fault.
what i would do is this..

1. Plug in laptop again, read and clear any codes stored
2. Turn laptop back off and let it charge
3. Start car and let it warm up a bit
4. Plug in the laptop and read codes again

That might sort it. Although the very fact it says its an intermittent fault would tend to suggest that it could be a wiring issue, poor connection somewhere or corroded bit of wire or something but try easy stuff first like just clearing out the codes and see if they come back or not.

dumbledore said:

Looks like you got genuine one and wiring should be fine.
You need now to check how bad the emissions are with the new lamda.
If CO is marginal fail, then the lamda is OK, but something else needs attention. Is the engine running good?

Click to expand...

As far as I can judge without means of testing it, the engine runs fine. I am going to try blu73 suggestions first, before I go back to the MOT shop to obtain CO readings. Many thx till so far.

blu73 said:

I suspect that is a stored code and not live fault.
what i would do is this..

1. Plug in laptop again, read and clear any codes stored
2. Turn laptop back off and let it charge
3. Start car and let it warm up a bit
4. Plug in the laptop and read codes again

That might sort it. Although the very fact it says its an intermittent fault would tend to suggest that it could be a wiring issue, poor connection somewhere or corroded bit of wire or something but try easy stuff first like just clearing out the codes and see if they come back or not.

Click to expand...

Ok, will do so and keep you guys posted.

Somewhere else I read that I should rev-up a couple of times to see if the lambda is reacting. I hope this will be visible when I make a grah in multiecuscan. Tbc as well.

blu73 said:

I suspect that is a stored code and not live fault.
what i would do is this..

1. Plug in laptop again, read and clear any codes stored
2. Turn laptop back off and let it charge
3. Start car and let it warm up a bit
4. Plug in the laptop and read codes again

That might sort it. Although the very fact it says its an intermittent fault would tend to suggest that it could be a wiring issue, poor connection somewhere or corroded bit of wire or something but try easy stuff first like just clearing out the codes and see if they come back or not.

Click to expand...

YEAH :worship: this was the trick. I removed the error codes and the lambda started working. Percentages were going up and down. Many thanks Blu73!