Network and Communication

Subsystems

• U00xx 116 Bus Signal and Bus Off The buses themselves — high and low speed CAN, LIN and single-wire links — reporting a signal fault or a bus that has shut itself down. A fault here affects every module hanging off it.
• U01xx 172 Lost Communication A named module has stopped being heard from. Rarely means that module has failed — its power, its earth, the bus wiring, or another module holding the bus down are all commoner.
• U02xx 165 Lost Communication (continued) The same family continued into a second block as the number of modules on a vehicle outgrew the first.
• U03xx 75 Software Incompatibility Modules that are talking but disagree about what they are talking to — mismatched software versions, calibrations that do not belong together, and configurations that do not match the vehicle.
• U04xx 181 Invalid Data Received The conversation is working and the content is wrong. A module is being heard clearly and sending values that cannot be true, which is a different fault from silence and often a harder one.
• U05xx 160 Invalid Data Received (continued) The same fault as U04xx — a module heard clearly, saying something that cannot be true — carried into the parts of the car people touch. Doors, seats, windows, roofs, mirrors and switches dominate this range, which puts most of it in the wettest, most flexed and most physically abused wiring on the vehicle, and a tail of converters, drive motors and battery sensors at the far end.
• U06xx 83 Lost Communication with Sensors and Actuators The third Lost Communication range, and the one where the thing that went silent is a part rather than a computer. Oil pressure sensors, coolant pumps and bypass valves, wastegate position sensors, air dams and HVAC actuators all appear here — components that used to be analogue and are now small networked devices, mostly on a LIN sub-bus. Which means a fault here is often in the master module or the single wire feeding a whole chain, not in the part the code names.
• U30xx 47 Control Module Power and Ignition Supply What every other module depends on before it can do anything: its own supply, its earth, and the ignition state telling it whether the car is off, accessory, on or cranking. Faults here are upstream of everything — a module with a poor earth reports nonsense about the parts it watches, so this range is where a page of unrelated codes across the whole car often begins.
• U35xx 73 Control Module Supply, Interlocks and Fuel Cell Three unrelated tenants sharing one block. It opens with the detail of control module supply that U30xx introduces — the range, low, high and intermittent variants of each input power circuit — then runs a long series of high voltage interlock circuits for electrified vehicles, and ends in hydrogen fuel cell hardware: tank temperature and pressure sensing, anode and cathode valves, and stack coolant. What unites them is only that the standard reached this range late.