I replaced msd 85 engine ecu on e70 5.0l x5 with boot mode. All good, start the car, test drive, fit all covers back. Ready for customer to take and when starting again it wanted to start but faild. stores code 2e77 igniton supply voltage. No spark, coils earth is ok voltage supply ok ecu does not puls coils. cheked ecu for soldering mistakes (none). No pinched wires. Annyone who can give good news.

Probably a damaged ( short) driver for some ignition coil.

Going to replace MSD85.1 ecu again, but can read old ecu . can I read/write isn without boot mode.

You can read by obd
If writing is needed then you need boot mode

Please forgive me. I felt so ashamed 9 months ago about my msd85.1 no spark problem. I couldn't tell you. After fitting back the engine covers and harness, i accidentally fitted the coil plug connector on dme the wrong way around. It slides in deep enough to think it is in, but it doesn't clip. I probably plug and unplug that one 7 times and 3 months later only found my problem.
So match for being a bmw technician!