No he's right. U means it's a network problem. Communication Area Network Buss or simply CAN buss. It's the Buss that all of the modules use talk to each other with.
It's like a highway with off ramps at each module where coded signals move from one module to another. Any module can talk to any other module on the buss at anytime, and indeed they are constantly. The signals are given certain priorities in order to keep everything from traffic jamming. The signals themselves get very complicated but the basic idea is pretty simple. If a high priority signal is on the network, all lower priority signals don't get sent. It's actually more complicated than that but that's the basic idea.
Those codes just mean the compass module is not talking on the network. Either it's on ramp to the highway is busted, which would be a wiring problem or the module is bad. Just a guess.
