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 (33)
P1698
Jeep · Powertrain
The engine computer stopped hearing from the transmission computer, often leaving the Jeep…
Moderate
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
U0102
Network
Other modules can't hear the 4WD transfer case module, so 4WD shifting is disabled.
Moderate
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
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
U0126
Network
Modules no longer receive the steering wheel angle, so stability control and lane assist switch…
Moderate
U0128
Network
The electronic parking brake module dropped off the network, so the parking brake may not apply…
Moderate
U0131
Network
The electric power steering module dropped off the network; steering assist may be reduced…
High
U0140
Network
Other modules stopped hearing from the body control module that runs lights, locks, wipers…
Moderate
U0141
Network
A body module labeled "A" went silent; on many trucks and SUVs it is the smart fuse box under…
Moderate
U0146
Network
The central gateway that links the car's networks went silent, so many modules report errors…
Moderate
U0151
Network
Other modules can't reach the airbag computer, so the airbags and seatbelt pretensioners may…
High
U0155
Network
Modules can't reach the instrument cluster, so gauges, warning lights and chimes may go dead.
Moderate
U0401
Network
The engine computer is still on the network, but another module doesn't trust the numbers it's…
Moderate
U0402
Network
The transmission module is online, but the gear, range or torque data it sends doesn't add up.
Moderate
U0404
Network
The electronic shifter reports a lever position the transmission can't trust, so Park may not…
High
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
U1000
Chevrolet · Network
A module on an older GM's Class 2 data line couldn't communicate, so modules stopped hearing…
Moderate