Failed MOT S40 T5

[LizardOfBodom]

Originally Posted by domhart10

Had to do the MOT again as its in a different garage now which I trust a bit more (Cant wait to move out of cornwal as I dont trust any garages here)

But they had to MOT it again just to check everything as a retest is free. But no I dont have vida or dice, probably something I should look at as well, are they easy to use?

Oh, Lambda sensor, tell me all about it :P just so happen I replaced mine on Tuesday so I can chip in the info. First of all my car actually threw out the CEL code inforiming me lambda is gone. Sensor was still working and oscillating between 0 and 1 as FM said, but clearing the code made it reappear every time again so there was still something not right.
Also agree on FM's advice - dont cheap on the sensor. If your rear one is gone (O2 sensor rear bank 1, as said on OBD reader) I guess its the same as mine as those were in use on all T5 models even FLs. Mine was OEM 30650109 (superceeded number, actually there were like 3 matching numbers) and the only thing I would recommend you is to get BOSCH 258 006 682 one. That is OEM one , not even "matching" one but actual OEM as per inscription on the actual sensor. I wouldnt consider any other brands as its fairly important piece and I wouldnt trust el-chaepo ones.
Bosch one was 75Eur from ebay. Plug & play.
I was considering a Bosch "universal" one (its the same sensor but with no socket so you have to do DYI wiring from your old one) its half the price but too much hassle and didnt feel its the right way to save money.
Replacing it made my CEL gone and car is happy again.

[domhart10]

Thread closed now and car done. Lambda sensors had to be replaced and now working fine (Replaced with Bosch ones) garage confirmed that cat does need replacing for next year, but with a new system coming that will all be solved.

[dingov70]

MOT tester here , chucking in a few pennies worth of knowledge .
1) Performance cats tend to require a good thrash to get hot & work properly first time of use & then work well once HOT !

2) Ask tester which readings were constantly changing , if it is the CO ( carbon monoxide ) , look at the Lambda sensor having become slow to react and then reading climb & fall even thought revs remain constant ( ish )

3) Demon tweeks are much loved by the motorsport community & try to avoid the jaunty hat angle crowd , been using them since early 80's