There is a reason you should only hold it to ground *while* powering up the ECU, not after.
Oh but I did. I tried everything. The only time the Galletto software didn't tell me that boot mode was inactive was when I left the pin connected to ground while the ECU powered up, and throughout the read. If I disconnected it before I initiated the read - nothing. It took me 2 days of trial and error to discover this.
But that makes sense why the resulting .bin after a Galletto read was garbled nonsense, because one of the pins was probably always outputting 0's. ha.