Passat TDI PD 115 - DIS Warning: ENGINE WORKSHOP!

[jojo]

Recently I've been getting the message 'ENGINE WORKSHOP!' on my DIS display along with the ignition coil symbol flashing away at me on the dash, can anyone shed some light on what it could be? The car runs perfectly in everyway whilst it's flashing away and beeping, and it only usually comes on in start-stop driving and soon disappears when the road opens up.
I've done a little bit of research, and some have suggested it's the brake light switch, which I have already changed. Other parts that have been changed on the car in the last 12 months is coolant sensor to cure high revving of the engine on start up and the MAF sensor due to fluctuation in power delivery.
The car also currently has the airbag light on, which is probably due to rusted terminals under the seat, I havn't got round to fixing this problem yet, but paid VW for the privilege 2 years ago, and it's just come back... is this related?
Other than these few niggles, my car has run like a dream and is currently on 136k miles with no major problems

 

[Caesium]

The brake light switch will put on the engine management lamp and will cause the car to go into limp.
I had this problem and it was the alternator.
Its unlikely that the airbag would cause the engine workshop display so I'd rule that link out.

 

[jojo]

I've sorted the airbag problem, but the 'Engine to workshop' is still coming up now and again, new brakeswitch and all brake lights working.. it's doing my head in!