Remove the cabin air filter, HVAC cowl and all covers in the way of accessing the ECU. You should only need an 8MM socket for this.

Remove the engine cover by removing the three screws that secure the it.

The oxygen sensor being replaced it tucked underneath this metal bracket.

The bracket is held in place by two very small E8 screws.

Loosen the metal bracket by removing the two E8 screws holding it in place.

With the bracket screws removed, simply wiggle the bracket free from the engine bay.

An offset O2 sensor wrench is highly recommended, due to the tight working area.

Fit the offset O2 sensor wrench over the sensor by feeding the wiring through the open slit on the wrench.

Using a ratchet, loosen the O2 sensor by turning counter-clockwise until it's fully freed from the engine.

Unplug the O2 sensor connector by pressing the retention tab down and pulling the connector apart.

The sensor can now be removed from the engine bay.

Apply a thin line of anti-seize lubricant to the threads of the new O2 sensor ensuring not to touch the sensing element on the end or get any anti-seize in the holes.

Hand-thread new O2 sensor into the engine. Once fully flush, torque the sensor down to 37-ft Ib.

Plug the new O2 sensor into place.

For cleanliness, neatly ziptie the O2 sensor cable and tuck it away.

Re-install the metal bracket back over the O2 sensor ensuring not to drop the small E8 screws.

Re-install all components in the vice versa of removal. i.e cabin air filter and cowl, covers, etc.

Reconnect your BMW's battery.

Using a BMW scan tool, clear all engine codes and confirm any O2 sensor related codes are gone.

Power on vehicle to test all electronics are functioning properly. Keep an eye on your dashboard for rough idling or check engine lights. If the check engine light is still present, connect a scan tool and troubleshoot further.

Good job replacing your O2 sensor! Be sure to keep an eye on your electrical system for any future issues.