OBD-II Trouble Codes: Meaning & Fixes
OBD-II trouble codes are five-character codes stored by your vehicle's computers when a monitored system goes out of range. Browse them by system (P, B, C, U), by sub-system or by the symptom you notice. Each code page explains what the code means, how serious it is, whether you can keep driving, the likely causes in order, how to diagnose it and what repairs typically cost.
648Codes
2.8Average severity
16%High or critical
18%DIY-friendly
Severity distribution
Most viewed
B0001
Body
The airbag module found a fault in the firing circuit for the driver's front airbag (stage 1).
High
P0135
Powertrain
The heater inside the upstream oxygen sensor on bank 1 isn't working or its circuit is faulty.
Low
P0174
Powertrain
The cylinder bank without cylinder 1 is running lean even with the maximum fuel correction…
Moderate
P0300
Powertrain
The engine computer sees misfires that jump between cylinders or hit several cylinders at once.
High
P0420
Powertrain
The bank 1 catalytic converter no longer stores enough oxygen to clean the exhaust properly.
Low
P0430
Powertrain
The bank 2 converter on a V6, V8 or split-exhaust engine isn't cleaning the exhaust well enough.
Low
All codes (410)
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
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
U1900
Ford · Network
A Ford module stopped receiving messages it expects from another module on the CAN network.
Moderate