Network Codes (U-Codes): Full List
Network codes start with U and mean that control modules have stopped talking to each other properly over the vehicle's data network, usually the CAN bus. A U code rarely points to a failed part on its own: weak battery voltage, a poor ground, corroded or loose connectors and water intrusion are common causes. Several U codes at once often share one root cause, so read them all before replacing anything.
42Codes
3.1Average severity
33%High or critical
5%DIY-friendly
Severity distribution
Most viewed
U0073
Network
A module saw so many errors on CAN bus A that it shut off its own transmitter.
High
U0100
Network
Another module stopped hearing from the engine computer on the CAN network.
High
U0121
Network
Other modules stopped receiving data from the ABS module, so ABS and stability control are off.
Moderate
U0001
Network
A module found the high-speed CAN network itself misbehaving, not just one silent module.
High
U0101
Network
The engine computer and other modules stopped hearing from the transmission control module.
High
U0151
Network
Other modules can't reach the airbag computer, so the airbags and seatbelt pretensioners may…
High
All codes (42)
U0415
Network
The ABS module is online, but the wheel-speed data it shares looks wrong to the other modules.
Moderate
U0416
Network
Stability-control data (steering angle, yaw rate) failed a plausibility check in another module.
Moderate
U0418
Network
Brake-control data such as pedal position or brake-assist status looks implausible to another…
High
U0420
Network
The electric power steering module is talking, but its steering angle or torque data doesn't…
Moderate
U0422
Network
The body control module is sending data other modules reject, often after a BCM swap or wiring…
Low
U1000
Chevrolet · Network
A module on an older GM's Class 2 data line couldn't communicate, so modules stopped hearing…
Moderate
U1000
Nissan · Network
A Nissan control module couldn't send or receive CAN messages for about 2 seconds or longer.
Moderate
U1064
Chevrolet · Network
Other modules stopped hearing the body control module on an older GM's Class 2 data line.
Moderate
U1096
Chevrolet · Network
Other modules on an older GM's Class 2 network stopped receiving messages from the gauge…
Low
U1900
Ford · Network
A Ford module stopped receiving messages it expects from another module on the CAN network.
Moderate
U3000
Network
A module has flagged a problem with itself: its memory, software, setup or internal electronics.
Low
U3003
Network
A control module saw its supply voltage drop too low or rise too high, usually a battery…
Low