Hi, My wifes 2004 xc90 diesel has recently had power issues. When driving the car suddenly loses power/acceleration. The message "engine system service urgent" pops up. The car still drives but greatly compromised. However if i stop the car and turn off the ignition the message goes away and drives normally. The light can come back again, there is not anything in particular that makes this happen. Any advice, has the engine management system broken or is it about to give up all together or is it the ETM?

I'd be grateful for any feedback.