Check engine light on: Codes, Causes & Fixes

A steady check engine light means the engine computer has stored a fault that affects emissions or engine management. In most cases you can keep driving normally for now, but have the code read soon – many auto parts stores and any OBD-II scanner can do this. If the light came on right after refueling, check that the gas cap is tight; loose caps are a classic trigger for EVAP codes.

558Codes

2.7Average severity

12%High or critical

18%DIY-friendly

Severity distribution

Most viewed

P0174 Powertrain The cylinder bank without cylinder 1 is running lean even with the maximum fuel correction… Moderate P0420 Powertrain The bank 1 catalytic converter no longer stores enough oxygen to clean the exhaust properly. Low P0101 Powertrain The MAF sensor's airflow reading doesn't match what the engine computer expects… Low P0113 Powertrain The intake air temperature signal is stuck at maximum voltage, which usually means an open… Low P0135 Powertrain The heater inside the upstream oxygen sensor on bank 1 isn't working or its circuit is faulty. Low P0171 Powertrain The engine computer is adding the maximum extra fuel it's allowed on bank 1 and still sees… Moderate

All codes (558)

All Severity 3+ Severity 4+

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 U0140 Network Other modules stopped hearing from the body control module that runs lights, locks, wipers… Moderate U0146 Network The central gateway that links the car's networks went silent, so many modules report errors… Moderate 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 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 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

Symptoms

Loss of power 214 Rough idle 184 Limp mode 165 Poor fuel economy 146 Engine stalling 133 Car won't start 123 Harsh or slipping shifts 80 ABS / traction light on 65 Fuel smell 34 Check engine light flashing 22