Hi all,
I've got the same problem as you...
Bought a 2nd hand avic f940bt.
Installed the 2013 maps (worked perfect after that)
Bought and installed the ui202navi for iphone 5 connectivity
Read that I had to update firmware to 5.1.
Put the firmwared on formatted sd-card
Here I used write all ucom data, instead of write ucom data.
So i saw two rows updating. and it was successful.
Then I waited, and waited... nothing happened... so I thought. ok lets try the "write ucom data".
It started writing again, but repeated it several times with a CS error.
Then the unit would