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
U0122
Network
Other modules lost contact with the stability control computer, so ESC and traction control…
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