Volvo 940 estae what does a sigin on the dash mean its orange back ground with green triangle and a black y upside down it only comes on when you are driving and you lose all power any ideas please?

The "upside down y" is a Greek letter Lambda. Volvo uses this symbol for their emission control system. The "Lambda Sensor" is an oxygen sensor in the exhaust system. I would look into a bad sensor. Good luck