The only time my 240 threw codes was when I crashed across a railway level crossing. I had one 240 owner in the car and another very experienced Volvo guy as well. We "limped" to our camp site a couple of miles further on and did some checking with code reader. Found some numbers but didn't have a check list. We disconnected the battery overnight and all was well in the morning when reconnected. Back to 1.1.1. We were going to leave it for 30 minutes and try again but went to the pub instead! Never had any further problems. 1992 model SE. We checked both of the readers, the main one on the battery side and the other small one on the other side. For me the battery disconnection fixed the problem so it might be the same for you.