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

24634 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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Thanks for your post and excellent photos.

On the N12 engine, I found it wasn't necessary to remove the heat shield. The 3 bolts securing the front face of the heat shield are also a real fiddly to reach too.

The new pre-cat O2 sensor comes with a male electrical socket which is fixed to the metal bracket. To unplug the cable, press the visible clip on front facing one side of the FEMALE plug and then gently ease it off by pulling upwards - make sure you grip the plug and don't try to pull on the wires! Then you will probably need to use a large flat bladed screwdriver to carefully lever the connector against the bracket, to separate them.

Now remove the 10mm bolt which secures the bracket to the oil filter housing. The post-cat cable will still be attached to the bracket, but you should be able to move the bracket and cable to one side, to improve access to the O2 sensor.

It wasn't too difficult to remove the O2 sensor using a Laser oxygen sensor socket, extended length extension bars, and 12" wrench.

We bought a new Bosch pre-cat O2 sensor from EuroCarparts for £115. Note that ECP do not list actual Bosch part numbers on their website, but Bosch do have a lambda sensor catalogue PDF which you can download to check exactly what is needed. I've uploaded a jpeg from their 2015 catalogue.


The actual Bosch part number is only printed on the new O2 sensor's cardboard box.

fwiw, for 1.6 N12:
long code 0258017217
short code LS17217

(We did find a code printed on the electrical connector on both old and new O2 sensors matched, but it didn't correspond to any Bosch catalogue part number.)

As far as I can tell from the catalogue, Bosch do not appear to make the post-cat sensor, and yet ECP offer a Bosch post-cat sensor. NTK may be the OEM for the post-cat sensor.

Forgot to add P2414 O2 sensor error kept appearing immediately after starting engine after erasing it a few journeys earlier. Engine with 40k miles ran fine. New sensor resolved problem.


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Here are photos of the O2 sensor I documented above which was removed from Mini just over 12 months ago.

The 57 plate Cooper is only used for short runs for past few years.

Quite a lot of soot on the sensor. In hindsight, I wonder whether we could have just cleaned it and refitted it to see if it would eliminate the P2414 error code.

In any case, the new sensor has not caused any problems.


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