I am working on replacing the rear o2 sensor on a 2005 Mini cooper S.
Can anybody tell me how to release the rear o2 sensor electrical connector ? Do I lift on a tab or press? Pictures would be very helpful if available.

 

Going to move you to the Stock Problems/Issues area.

Below is a video on the rear o2 but they do not have any details on disconnecting the plug. IMO based upon working on my MINIs, there use two types of plug connections, either a pull tab similar to the coil plug or a push in and pull tab similar to the turn signal/fog lights.

 

Figured it out. Two steps.

Rear o2 sensor connector removal.

The connector body for the sensor side of the harness is anchored to the body on a plastic channel. First disengage the lock which prevents sliding the connector assembly off of the channel. I used a very small screwdriver to push the finger lock to one side. Slide the connector assembly forward toward the front of the car. Once the connector assembly is free, press on a tab which allows the sensor side connector to disengage from the harness connector.

Inspection of the replacement connector should make my instructions a bit more clear. Sorry, no pictures.