The exclamation mark seems to mean you have a standing fault with an ECU - likely the engine ECU,
I had it recently when my throttle pedal was playing up: EPC light on, 'Engine Fault - Workshop' up on the DIS, Exclamation mark by the cruise indication and no boost available - limp mode.
It would come in/out...and with every exclamation mark came limp mode.
If you get your faults scanned you should be able to work out what's causing it.