Alfa 147 1.6 Tspark Immobiliser Fault displayed
I have just had the same problem after my Alfa 147 1.6 tspark had been standing on the drive 2 months and the inevitable low/flat battery.
It bump started in reverse down the drive, great I thought, and on to the garage I went, to have rear discs and pads fitted.
Once the work was complete the garage informed me of the above fault being displayed on the dash. They hooked up the diagnostic, cleared the fault, then it would re-appear when trying to start the engine.
We had jump leads connected to the battery for that extra assistance, but still no joy with the displayed fault.
I then read in another forum that another way to resolve this problem is to remove the negative terminal of the battery for approx 15 mins, and this will clear the memory in the ECU hence removing the alleged fault.
I probably left the negative terminal off for about an hour, and once re-attached, BINGO, the car started up first time.
Hope this helps out fellow Alfa owners as this seems an inherant pain in the backside, but easily rectified when you do the above. Happy motoring.