Unless the codes changed, a 113 & 115 code are injector group codes. An O2 code would be 212. Who told you that 113 was an O2 code? Whatever you do don't unplug the AMM while the engine is running or you will have an expensive experiment. One area to check is the relay plug the provides power to the fuel injectors. There are two relays both indentical located on the driver's side of the engine compartment next to the big black cover. The one with the red wire powers the injectors and make sure the connectors on the plug are making good contact with the pins on the relay. This may not correct your problem but I can tell you from expereience a poor connection at the relay will drive you nuts trying to find the problem. Lots of mechanics (dealership and Volvo specialist) didn't find this one. Good Luck and let us know what you find. It could always be something that no one has experienced before.