OBD2 code lookup
Your mechanic or a free scanner at AutoZone gives you a code like P0420. Here's what it actually means — in plain English.
Check engine light on? Get a free code scan
If your check engine light is on, most auto-parts stores (AutoZone, O'Reilly, Advance) will read the code for FREE — no purchase required, just walk in. Bring the code back here and look it up at eli5cars.com/obd2 for the plain-English explanation.
Note: a scan only helps when there's an active fault code. For purely mechanical symptoms (noises, vibrations, leaks), a scan may show nothing — the suspects listed above are your starting point.
P0011P0011 Code: Camshaft Position Timing Over-Advanced or System Performance (Bank 1)
moderateP0016P0016 Code: Crankshaft/Camshaft Position Correlation (Bank 1, Sensor A)
highDon't driveP0017P0017 Code: Crankshaft Position – Camshaft Position Correlation, Bank 1 Sensor B
moderateP0101P0101 Code: Mass Air Flow Sensor Range/Performance Problem
moderateP0102P0102 Code: Mass Air Flow (MAF) Circuit Low Input
moderateP0113P0113 Code: Intake Air Temperature Sensor Circuit High Input
lowP0128P0128 Code: Coolant Temperature Below Thermostat Regulating Temperature
lowP0131P0131 Code: O2 Sensor Circuit Low Voltage (Bank 1, Sensor 1)
moderateP0133P0133 Code: O2 Sensor Circuit Slow Response (Bank 1, Sensor 1)
lowP0135P0135 Code: O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 1)
moderateP0155P0155 Code: O2 Sensor Heater Circuit Malfunction (Bank 2, Sensor 1)
moderateP0161P0161 Code: O2 Sensor Heater Circuit Malfunction (Bank 2, Sensor 2)
lowP0171P0171 Code: System Too Lean (Bank 1)
moderateP0174P0174 Code: System Too Lean (Bank 2)
moderateP0201P0201 Code: Cylinder 1 Injector Circuit Malfunction/Open
moderateP0300P0300 Code: Random Multiple Cylinder Misfire Detected
moderateP0301P0301 Code: Cylinder 1 Misfire Detected
moderateP0302P0302 Code: Cylinder 2 Misfire Detected
highDon't driveP0303P0303 Code: Cylinder 3 Misfire Detected
moderateP0304P0304 Code: Cylinder 4 Misfire Detected
highDon't driveP0306P0306 Code: Cylinder 6 Misfire Detected
highDon't driveP0332P0332 Code: Knock Sensor 2 Circuit Low Input (Bank 2)
moderateP0335P0335 Code: Crankshaft Position Sensor Circuit Malfunction
highDon't driveP0340P0340 Code: Camshaft Position Sensor Circuit Malfunction
highDon't driveP0344P0344 Code: Camshaft Position Sensor Circuit Intermittent (Bank 1)
moderateP0401P0401 Code: Exhaust Gas Recirculation (EGR) Flow Insufficient
moderateP0420P0420 Code: Catalyst System Efficiency Below Threshold (Bank 1)
lowP0421P0421 Code: Warm Up Catalyst Efficiency Below Threshold (Bank 1)
lowP0430P0430 Code: Catalyst System Efficiency Below Threshold (Bank 2)
lowP0431P0431 Code: Warm Up Catalyst Efficiency Below Threshold (Bank 2)
lowP0440P0440 Code: Evaporative Emission Control System Malfunction
lowP0442P0442 Code: Evaporative Emission System Leak Detected (Small Leak)
lowP0446P0446 Code: EVAP Vent Control Circuit / System Malfunction
lowP0449P0449 Code: Evaporative Emission System Vent Valve/Solenoid Circuit Malfunction
lowP0455P0455 Code: Evaporative Emission System Leak Detected (Large Leak)
lowP0456P0456 Code: EVAP System Very Small Leak Detected
lowP0507P0507 Code: Idle Air Control System — RPM Higher Than Expected
moderateP0521P0521 Code: Engine Oil Pressure Sensor Range/Performance Problem
highDon't driveP0603P0603 Code: Internal Control Module Keep Alive Memory (KAM) Error
lowP0606P0606 Code: PCM/ECM Processor Fault (Internal Control Module Performance)
highP0700P0700 Code: Transmission Control System Malfunction
highDon't driveP2195P2195 Code: Oxygen Sensor Signal Stuck Lean (Bank 1 Sensor 1)
moderateP2197P2197 Code: Oxygen Sensor Signal Stuck Rich (Bank 2 Sensor 1)
moderate