What changes
Central electrics 09 long coding, byte 2, bit 3 = 1 (sl_at_drl). In daytime the rear position lights come on together with the daytime running lights.
Details
The car is easier to see from behind at dusk, in rain and fog before the automatic lights switch the headlights on. To turn off, set the same bit to 0. A long coding parameter of the MLB Evo central electrics unit (J519). One bit changes, the other bytes stay. 09 coding on MLB Evo usually needs no access code; from model year 2019 the unit may accept changes only with the bonnet open. If the unit is SFD-protected, a3c warns before writing.