Lambda Sensor Issue -- Remap

[rafa_vtc]

Hi guys,

I'm leaving the car with Aonghus for a remap this Friday and while doing all the health checks and servicing I found out that my lambda sensor fitted on the header is actually disconnected. There is a female plug also loose which I would assume is the one for the lambda but they are quite different, even one has three pins and another one has two.

There is also another sensor which is plugged on the downpipe.

When I look for new sensors they seem to have the same connection plug as the one I have now, so I don't know if there is any point in buying one of them. Any suggestions or ideas? Could be that the one on the downpipe is doing the work and I don't need the one in the header anymore? Or just lazy previous owner that didn't buy the proper one and left it disconnected. Car runs pretty good in fairness.

Many thanks in advance.

 

[Fozzy]

One is pre-cat and used for closed loop fuelling (it also has some input into open loop afr calculations as far as I know) one is post cat and covers emissions. The latter will not have an effect on the running of the car apart from a CEL

The former can cause major issues if faulty and plugged in but the car will run fine with it plugged out albeit a bit rich.

Has the car been mapped already with them plugged out? Hard to see it passing NCT emissions with no O2 sensors and no map to compensate ?

 

[rafa_vtc]

Thanks Fozzy, I think in my case both are actually pre-cat, that's why I wonder if the one on the downpipe is doing the work (located on top side right after turbo) and the one in the header is not needed anymore. Car hasn't been mapped and flew through NCT last two years without any problems.

 

[Fozzy]

Sounds like something has been changed alright. My car only has one o2 located on the downpipe straight after the turbo and before the cat. Usually if there?s one in the header, the other is after the cat so maybe someone has moved the o2 on the downpipe or fitted a different downpipe and is just running off that one?

Either way if it?s running fine and passing NCT I?d say fire away - Aonghus won?t blow it up for sure

 

[rafa_vtc]

Yes, that makes sense. I think I might have either older header/heads or newer downpipe than I should, that's why the two lambdas. I hope there is not many more messy stuff so Aonghus doesn't find an awkard puzzle to deal with.

Thanks Fozzy for your very helpful replies.