BMW E90 Comfort Access key and antennas
How do you replace the battery in a BMW E90 Comfort Access key?
The key has a battery, not a rechargeable cell, so the ignition lock does not charge it. Remove the key blade from the key, open the cover with a flat screwdriver and replace the battery. A CR2032 battery is suitable.
Why does Comfort Access work poorly or intermittently?
Replace the key battery first. Next check the antenna wiring. A common source of faults is the Comfort Access antenna inside the rear bumper (part number 61356922212), which also gives a fault code. Coins in the cup holder in the centre console can interfere with the key's signal.
Does the rear bumper have to be removed to replace the Comfort Access antenna?
Not on the E91. The antenna is under the rear bumper in the centre, held by plastic clips, and no tools are needed to remove it.
Why does the third Comfort Access key not work keylessly?
Only two Comfort Access keys can be active on a car. The third works as a normal key, unless a previously programmed, usually lost, key has been deactivated. The number of active keys can be seen with a diagnostic device.