612 Scaglietti Engine Management Gremlin

[fitzmoresco]

My 612 engine management light comes on and stays on when cruising at 90-91mph in 6th. It doesn't reset when turned off and back on. It has been back to the dealership several times but they are stumped so far? Diagnostics indicated a mis-fire on a specific cylinder but with no loss of power it is a false signal and they've even spoken to Bosch without any luck. Car runs beautifully and recently ran it there and back flawlessly round the Nurburgring. Any similar problems or better still solutions welcomed