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Cat and sensor replacements

4K views 8 replies 4 participants last post by  mike1967 
#1 ·
Hello,

I've had a P00420 code thrown up by the car - an R56 Mini One 2007 (2/2) - and so I took it to the garage for an MOT to see exactly whats wrong. I was told I need a new cat and two new sensors. The car failed on emissions and the sheet is attached. With this info can anyone tell me which two sensors I need? I have been looking on Euro Car Parts and found the correct cat but there are a few variations of sensors. Any help appreciated.

I am planning on replacing it myself. I'm a first-year automotive engineering student and would like to get involved with my car a bit! Any tips?

Cheers.
 

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#2 ·
welcome to the is the emissions failure due to sensors or the sensors are part of the issue or they are picking up another problem.
another problem would be timing chain stretched, if car over 60.000 miles then i would say this is most of the problem or cause of the problem, what happens when chain stretches it alters the over lap on the valves this is turn makes it run rich or lean depends on what cycle cam is on at different temperatures,, i always recommend to people these things tend to go hand in hand with these engines any need to repair the cause rather than the outcome if that makes sense. i done a 64.000 miles 1.4 the other day on a 58-plate full service history car low miles, had to do chain and both 02 sensors and after a dose of cataclean,,
or if you just want to get it through mot put a can of cataclean in no more than 1/4 tank of fuel take it for 4000 revs drive for 20 miles and more than likely it will fool the gas machine mot in a bottle,
if you have access to diagnostic that can show a legend for vanos timing and actual timing you can clearly see chain stretched autocom cdp plus will do this,, the other way is remove or use a small camera and look at cam chain tension-er inside rocker box, if got more than 10mm showing chain is well on its way, or over 60k at 90k its always totally toast
 
#3 ·
It's on about 120,000... guessing I might need to check that timing chain.
I've had some work done which involved the removal of the timing chain, would they likely have tensioned it then?
I'm only expecting to have the car for another year really, hoping to change car late this year if all goes well.
With new cat and sensors is it worth sorting the chain?

Thanks for the reply.
 
#4 ·
I think you're missing what Mike is saying,

The cat may be ok, address the chain first, it 'may' need sensors he says, but the chain is making the engine run poor, putting a newer cat on won't change the way the engine is running as it's just a filter, so it likely will read the same?

The HC's reading high I'd guess is less likely to do with cat or sensors with only a minor CO rise, so I suspect he is spot on, cam timing affecting HC's. Chances are the CO will passively drop when this is fixed.

So your question should be the other way round ie: 'With new chain, is it worth sorting the cat and sensors' ;O) The answer is possibly no, just run the car as he said, which will clean stuff out, then get another cat test done, work with the results of that perhaps?

Only my2p
 
#5 ·
could not of said that better with 120k it will will coming up for its second chain kit if not had one already
 
#9 ·
yes any mapping company can pull bin file from self check on ecu
 
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