I have a 2005 MINI Cooper S with 125000 miles. Got a service engine light and my code reader kicked back a code PO138. Seems like I need to replace the number 2 oxygen sensor. It has never been replaced before. Was wondering if an aftermarket sensor on Amazon ($28.79) is sufficient enough quality vs. dealer part ($250.00) ? Also, should I buy a rethread tool to "clean the treads" after I remove the old one? Also, it looks very easy to replace by the YouTube videos I have watched, any suggestions before I start the job?
Thank you in advance !!!

or is it not necessary?

 

From what I understand the post cat O2 sensor is not as finicky as the pre cat O2 sensor. That being said the most reliable seems to be the NTK/NGK sensor then the BMW part. When I replaced my sensors I went with the NTK/NGK sensors as i found them for $110 each from Summit Racing.

 

I think they are less than that on RockAuto.

 

Yes you can find some brands for less then what I paid for the NTK/NGK O2 sensors. I was replacing both sensors and the pre cat sensor is the more picky sensor. I replaced both at the same time so I was worried more about direct fitment.

If you replace the pre cat sensor then the only two that are recommended to be trouble free are the NTK/NGK and BMW. Most others seem to be a crap shoot and generally throw some codes.

 

Bought the #2 sensor for $28.79 ( Kwiksen Heated O2 Oxygen Sensor from Amazon),
Oxygen Sensor Removal Tool for $11.75, the Tread chaser for $8.28.
So I have a total of $48.82 invested vs. about $400.00 quote from the rip off dealer.
I cleared the codes with my $29.00 Veepeak code reader and it runs perfect with no codes showing.
Very simple repair. The old sensor came out so easy I really did not need the special socket & the tread chaser. I sprayed penetrating fluid on the sensor over a 48 hour period while it was on jack stands and I think that made all the difference.
Nice to have the MINI back running well.

 

Nicely done. Congrats.

 

Just got this code on my way to work, hit Amazon for the part listed above and found one for $19 same part number and everything but doesn't specify upstream/downstream. The $28 item specifies downstream. I ordered the $28 sensor just because but I am curious, are they interchangeable?

 

Yes the sensors are interchangeable between locations.