My "Check engine" light has been on for 4 years (96, 850). When it first went on I took it to a Volvo dealer and he told me it was one of 4 EGR sensors that "may" be bad. I asked if it was something I should be concerned about and he said it will have no influence on the cars performance or the engines reliability - and thats comeing fro a dealer! I checked with 3 other shops that specialize in Volvos and they basically said the same thing. I have not had a problem. One thing to note - dependeding on where you live, annual state inspections require that the car passes emmission levels and can not have a "Check Enigine" light on. A simple fix - disconect the battery and reconnect in 10 minutes. This erases the memory for about 200 miles - the "Check Engine light goes away for a short while - long enough to get her inspected (and figuer out how to re-program your radio). Good Luck!