EDC warning light on MAN LE150C (D 0824 LFL engine)

ged:

AF1:
… check the fuel is good

Oh - how do I do that? The fuel has been in there for over four years, but I did’t think diesel had any problems like you can get with old petrol.

The engine starts and runs fine. No smoke, ticks over like one just out of the showroom.

I meant to just have a look in the tank for water or corrosion but if its running well I’d imagine it’ll be ok.
You can’t read the fault codes through the dash like you can on the later stuff it needs plugging into a computer.