Draining DEF E90

Remove the filler connection cap on the left rear bumper.
When draining the active tank, remove the filler cap (1); for the passive reservoir, remove the filler cap (2).
If necessary, use the screwdriver handle (3) from the onboard vehicle tool kit to open the filler caps.

Fig 1: Removing Filler Cap Using Screwdriver Handle
Courtesy of BMW OF NORTH AMERICA, INC.
Remove the cover under the left rear bumper to access the service ports for the active (1) and passive tanks (2).

Fig 2: Identifying Left Rear Bumper Service Ports For Active And Passive Tanks
Courtesy of BMW OF NORTH AMERICA, INC.
Connect the extraction line (1) from the tool (P/N 81 39 2 153 908) to the active (2) or the passive (3) service ports.
NOTE: Clean the caps for the service ports with water before reinstalling. Make sure the caps lock back onto the service ports

Fig 3: Connecting Extraction Line To Active Or Passive Service Ports
Courtesy of BMW OF NORTH AMERICA, INC.
Connect the shop air to the vacuum block, and open the valve at the vacuum block on the canister for vacuum supply. Slowly open the valve of the suction line at the canister and draw off the DEF. Watch the level through the level tube. Make sure the exhaust hose off the vacuum block is situated so that it will drain into a suitable catch pan, in case the DEF extractor canister gets overfilled.