The keypad is pretty close to the PC5108 board (10 cm). That is why the key bus is connected in daisy chain.
I disconnected the keybus on the PC5108 board, reset power, 902 + 903 commands. It displayed Keyboard 8 (without the Zone 9-12 and Zone 13-16). The Gen Sys Supv fault disappeared.
I reconnected the PC5108 board, reset power, 902 + 903 commands. It displayed Keyboard 8, Zone 9-12 and Zone 13-16. The Gen Sys Supv fault occured again.
Can it be a failure of the PC5108 board?
I checked the Keybus voltage on the PC5108 board. It seems OK (Vred-black = 13.5Vdc ; Vyellow-green = 2Vdc and 11Vac). All the sensors are in short circuit (all doors/windows closed, unused inputs short circuited)
You can see the PC5108 board: http://imgur.com/d14kCsv