There's a power supply before the ecu called the IVM. It's an all in one unit. That will cause the car not to start if it's fried. Also our wires to the ecu are completely exposed it's best not to hit the connectors directly with water but all detailers should know to wrap modern engines electric parts.
https://bmwtechnician.com/2019/07/29...-modification/
Check the current on the IVM. Also I'm not recommending you cut your IVM open, the link is more of visual for you
__________________
535i MIssion Performance, PS2, Helix HPFP Kit, Wagner FMIC, Spec 3 clutch, Steel SMF, Wolf Racing CP, UUC SSK, GFB dv, SprintBooster, Custom Dynomax Exhaust, M5 Sways, Eibach OE Springs, Koni Sports Adjustable, Custom Short Ram CAI
IG: @bmwdoubles