How about checking the engine. Then call a Volvo shop to diagnose the problem. This is not a DIY job. I know a lot of Volvo techs. Most of us drink beer. Try a friday afternoon around 3:30. Show up with some good brewskis and save $50.00. Otherwise spend around $10,000.00 for test equiptment, and $2500.00 for manuals, and save money by doing it yourself.

This message brought to you by a 23 year Volvo mechanic was not intended to be harsh, but to induce reality regarding this question. Don't go disconnecting the battery, and on and on. Certain problems WILL burn the car TO THE GROUND!!!! Don't play with fire. If you are in my neighborhood, I will read the code(s) for FREE. (Bay Area) (if you are a dot commie, I retract my last statement.)