Power Loss in Fiat Ulysse 2.0 JTD 1997 Diesel?

The EBOD warning light on the dashboard comes "on" and "off". In accordance with the Owner's Manual, this system is not installed in the diesel models. However, when it illuminates, there is usually a loss in power and the engine will not exceed 3000 rpm (in any gear). On a few occasions, when the light came "on", the engine went dead. Despite referring the problem to a Fiat maintenance centre, this problems continue to persist. Their electronic diagnosis cant find or fix the problem. How can it be fixed ?