It should not be necessary for any "read" operations such as monitoring or logging measuring values; it generally only blocks "write" operations.Indeed for some latest VAG cars bonnet has to be opened (bonnet switch triggered) to access diagnostic functions.
P.S. Interesting, what is a official dealer's procedure for monitoring/logging data from vehicle in motion...???
It certainly can't hurt, and isn't terribly difficult or expensive.Should I try again with the bonnet open?
I think once the hood has been opened and you've done something that requires write access, write access will remain available for a period of time (or miles?) even with the hood closed again...?Note: I subsequently reversed a coding change with the bonnet closed.