Check-engine trouble codes
Plain-English meanings for the most common OBD-II codes, how serious each one is, and the usual causes. Type a code like P0420 into the home page search to jump straight to it.
AD SLOT 1 (placeholder)
C12xx
C13xx
P00xx · Fuel, air & cam timing
- P0010 'A' Camshaft Position Actuator Circuit (Bank 1)
- P0011 'A' Camshaft Position - Timing Over-Advanced or System Performance (Bank 1)
- P0012 'A' Camshaft Position - Timing Over-Retarded (Bank 1)
- P0014 'B' Camshaft Position - Timing Over-Advanced or System Performance (Bank 1)
- P0016 Crankshaft Position - Camshaft Position Correlation (Bank 1 Sensor A)
- P0017 Crankshaft Position - Camshaft Position Correlation (Bank 1 Sensor B)
- P0021 'A' Camshaft Position - Timing Over-Advanced or System Performance (Bank 2)
- P0087 Fuel Rail/System Pressure - Too Low
- P0090 Fuel Pressure Regulator 1 Control Circuit Open
P01xx · Fuel & air metering
- P0101 MAF Circuit Range/Performance
- P0102 Mass Air Flow MAF Circuit Low
- P0103 Mass Air Flow MAF Circuit High
- P0111 IAT Sensor 1 Circuit Malfunction
- P0112 Intake Air Temperature Sensor 1 Circuit Low Input
- P0113 IAT Sensor 1 Circuit High Input
- P0116 ECT Sensor Circuit Range/Performance
- P0117 ECT Sensor Circuit Low Input
- P0118 Engine Coolant Temperature Sensor Circuit High Input
- P0121 Throttle Position Sensor/Switch A Circuit Range/Performance Problem
- P0122 Throttle Position Sensor/Switch A Circuit Low Input
- P0123 Throttle Position Sensor/Switch A Circuit High Input
- P0128 Coolant Thermostat (Coolant Temperature Below Regulating Temperature)
- P0131 Oxygen Sensor Circuit Low Voltage (B1S1)
- P0132 O2 Sensor Circuit High (Bank 1 Sensor 1)
- P0133 Oxygen Sensor Circuit Slow Response
- P0135 Oxygen O2 Sensor Heater Circuit Malfunction
- P0136 O2 Sensor Circuit Low Voltage (B1S2)
- P0138 O2 Oxygen Sensor Circuit High (B1S2)
- P0141 O2 Sensor Heater Circuit Malfunction
- P0151 O2 Sensor Circuit Low B2S1
- P0152 O2 Sensor (High Voltage) B2S1
- P0155 O2 Sensor Heater Circuit Malfunction (B2S1)
- P0156 O2 Sensor Circuit Malfunction B2S2
- P0161 O2 Sensor Heater Circuit (Bank 2 Sensor 2)
- P0171 System Too Lean Bank 1
- P0172 System Too Rich (Bank 1)
- P0174 System Too Lean (Bank 2)
- P0175 Engine Too Rich (Bank 2)
- P0190 Fuel Rail Pressure Sensor 'A' Circuit
- P0193 Fuel Rail Pressure Sensor 'A' Circuit High
P02xx · Fuel injectors & turbo
- P0201 Cylinder 1 Injector Circuit Malfunction
- P0202 Cylinder 2 Injector Circuit Malfunction
- P0203 Cylinder 3 Injector Circuit Malfunction
- P0204 Cylinder 4 Injector Circuit Malfunction
- P0208 Cylinder 8 Injector Circuit Malfunction
- P0234 Turbocharger/Supercharger 'A' Overboost Condition
- P0261 Cylinder 1 Injector Circuit Low
- P0264 Cylinder 2 Injector Circuit Low
- P0267 Cylinder 3 Injector Circuit Low
- P0270 Cylinder 4 Injector Circuit Low
- P0299 Turbocharger/Supercharger A Underboost Condition
P03xx · Ignition & misfire
- P0300 Random/Multiple Cylinder Misfire Detected
- P0301 Cylinder 1 Misfire Detected
- P0302 Cylinder 2 Misfire Detected
- P0303 Cylinder 3 Misfire Detected
- P0304 Cylinder 4 Misfire Detected
- P0305 Cylinder 5 Misfire Detected
- P0306 Cylinder 6 Misfire Detected
- P0308 Cylinder 8 Misfire Detected
- P0320 Ignition/Distributor Engine Speed Input Circuit
- P0325 Knock Sensor 1 Circuit Malfunction
- P0330 Knock Sensor 2 Circuit Malfunction (Bank 2)
- P0335 Crankshaft Position Sensor A Circuit Malfunction
- P0336 Crankshaft Position Sensor Range/Performance
- P0340 Camshaft Position Sensor Circuit Malfunction
- P0341 Camshaft Position Sensor Circuit Range/Performance
- P0345 Camshaft Position Sensor Circuit Malfunction Bank 2
- P0351 Ignition Coil A Primary/Secondary Circuit Malfunction
- P0352 Ignition Coil B Primary/Secondary Circuit Malfunction
- P0353 Ignition Coil C Primary/Secondary Circuit Malfunction
- P0354 Ignition Coil D Primary/Secondary Circuit Malfunction
P04xx · Emissions (EGR, catalyst, EVAP)
- P0401 Insufficient EGR Flow
- P0404 Exhaust Gas Recirculation Circuit Range/Performance
- P0411 Secondary Air Injection System Incorrect Flow Detected
- P0420 Catalyst System Efficiency Below Threshold
- P0430 Catalyst System Efficiency Below Threshold (Bank 2)
- P0440 Evaporative Emission Control System Malfunction
- P0441 Evaporative Emission Control System Incorrect Purge Flow
- P0442 Evaporative Emission Control System Leak Detected (small leak)
- P0446 Evaporative Emission Control System Vent Control Circuit
- P0455 Evap System Large Leak Detected
- P0456 Evaporative Emissions System - Small leak detected
- P0457 EVAP System Leak Detected (Fuel Cap Loose/Off)
- P0496 EVAP Flow During Non-Purge Condition
P05xx · Speed, idle & oil pressure
P06xx · Computer & output circuits
P07xx · Transmission
P0Axx
P20xx · Diesel aftertreatment
P24xx
P25xx · Turbo control
P30xx
P32xx
AD SLOT 2 (placeholder)