Engine management light??

Hi all hope someone can help, i have a Citroen Picasso 1.6 LX 2001, my Engine management light has come on in the last couple of days but the car is still driving ok, a mechanic friend put it on his computer and the message ECU fault/failure came up he advised me to think about getting rid but carry on driving it while it is still working? another friend in England spoke to his mechanic and he advised that if the car is still driving ok then it could be a loose wire or sensor? can anyone help.
Cheers