Module Communication Trouble Codes: List & Fixes
Module communication codes, such as U0100 (lost communication with the engine control module) or U0121 (lost communication with the ABS module), mean a module did not receive expected messages on the data bus. Start with the basics: battery voltage, grounds, fuses and connectors, especially where water can get in. Aftermarket accessories spliced into the wiring can also disturb the network.
43Codes
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
All codes (14)
U0001
Network
A module found the high-speed CAN network itself misbehaving, not just one silent module.
High
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
U0101
Network
The engine computer and other modules stopped hearing from the transmission control module.
High
U0103
Network
The electronic shifter (dial, knob or joystick) stopped talking to the transmission and engine…
High
U0105
Network
The PCM lost contact with the separate module that fires the injectors, common on diesel…
High
U0107
Network
The engine computer can't reach the module that drives the electronic throttle, so power is cut…
High
U0109
Network
The PCM lost contact with the module that controls fuel pump speed; stalling or no-start can…
High
U0110
Network
The hybrid/EV system lost contact with the module that runs electric drive motor A.
Critical
U0115
Network
Modules lost contact with the second engine computer on vehicles that use two of them.
High
U0131
Network
The electric power steering module dropped off the network; steering assist may be reduced…
High
U0151
Network
Other modules can't reach the airbag computer, so the airbags and seatbelt pretensioners may…
High
U0404
Network
The electronic shifter reports a lever position the transmission can't trust, so Park may not…
High
U0418
Network
Brake-control data such as pedal position or brake-assist status looks implausible to another…
High