How do I do a flash reset on a Berlingo ECU?

My father in law's been advised by Citroen that his ECU needs replacing. This is due to the "stop" light constantly flashing on his dashboard. I'm assuming this is the engine management light. I've had a look on the internet, as Citroen have obviously quoted a ridiculous price for the work, and there seems to be a couple of things I could try first. Does anyone know how to carry out a flash reset on the ECU? It seems there is a separate ECU for the engine and one for the dashboard and as the car is running just fine I'm assuming it's the dashboard ECU that's faulty and not the engine ECU. Can anyone help?