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How To: Change Pre-Cat O2 Sensor on Non-S R56 Cooper

24635 Views 4 Replies 3 Participants Last post by  calorgas
I've just changed the pre-cat O2 Sensor (Lamda) on my non-S R56 Mini Cooper 2008. The sensor had done 67,000 miles and early symptoms of failure, before the engine light came on, was that the car would run rough or even stall during weather below 10 degrees C. Normal engine codes for the pre-cat sensor were displayed.

A new Bosch 02 sensor from GSF Car Parts was £118+ VAT. I also picked up the Laser 22mm deep socket with a cut out to make the job easier - £11.

The images in the Haynes manual were poor. The image below shows the exhaust heat shield removed - 3x 10mm bolts on top and 3x 10mm bolts along the front (used a ring and open ended spanner to get off).

Once the shield is off you can see the sensor at the top - i have used a red arrow to show where it was after I had taken mine out. The sensor's connector was a bit fiddly and I took its mounting off of the oil filter housing to make it easier - single 10mm bolt.

This is the deep socket with the cut out and the original sensor in it.

The whole job took me 80 minutes and that included resetting the engine light with my OBDII scanner. The car now runs soooo much better...:big_grin:

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I replaced the pre-cat O2 sensor on my '07 Cooper today using the instructions just above (photos no longer showing on the original post). It is a bit fiddly as there's not a lot of room down there but I managed it without removing the heat shield as well, took me just about 45mins start to finish. The most difficult bit was getting the old sensor socket off the bracket, as it was really well wedged on!

The tool I did find very useful was my head torch, as even doing this outside on a bright day I struggled to see into the dark corners without it. I also bought one of the 22mm O2/lambda removal sockets from ebay, seemed to do the job ok.

Car drives a lot better with the new one though a bit concerned that the old one looked a bit sooty, hoping that that's related to the previous inlet vanos failure.
Ah yes, that's pretty much what mine looked like. Apparently you can clean them by immersing the business end in petrol for a few hours followed by a gently tickle with a soft brush. I may give the old one a bit of a clean and then stick it in a box in the shed...just in case of future need.

Anyway I have my firmly fingers crossed that the new sensor will mean no return of the P2414/P2626 codes I was getting, I live in fear of that "boo-be-doop" noise that accompanies a new dashboard alert. Gettin' twitchy.
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