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
P0302
Powertrain
Cylinder 2 keeps misfiring. On inline engines it's a middle cylinder, so rule out coolant…
Moderate
P0174
Powertrain
The cylinder bank without cylinder 1 is running lean even with the maximum fuel correction…
Moderate
P0011
Powertrain
The bank 1 intake cam sits further advanced than the PCM asked for, usually an oil or control…
Moderate
P0301
Powertrain
Cylinder 1 is repeatedly failing to fire. The cause is almost always its coil, plug, injector…
Moderate
P0021
Powertrain
The bank 2 intake cam is more advanced than commanded or slow to respond; compare it with bank…
Moderate
P0014
Powertrain
The bank 1 exhaust cam won't follow its target and stays too far advanced; think oil, valve…
Moderate
All codes (648)
U0156
Network
The main information display or head unit dropped off the network; screen, radio or camera may…
Low
U0164
Network
The climate control module dropped off the network, so heat, A/C, fan or defrost may stop…
Low
U0199
Network
The door module (usually the driver's door) went silent; windows, mirrors and locks on that…
Low
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
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