Check engine light on? Look up any code or warning light.

Plain-English explanations of 88 common OBD-II engine codes and 20 dashboard warning lights: what they mean, how serious they are, and what to do next.

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Misfire codesFuel & air codesEmissions, EVAP & catalystSensor & timing codesIdle, computer & transmissionDashboard warning lights

Popular

P0420
Catalyst System Efficiency Below Threshold (Bank 1)P0300
Random/Multiple Cylinder Misfire DetectedP0171
System Too Lean (Bank 1)P0455
Evaporative Emission System Leak Detected (Large Leak)Check engine lightFlashing check engine light

Warning lights

Check Engine Light (Solid)
mediumFlashing Check Engine Light
highOil Pressure Warning Light
highBattery / Charging System Light
highEngine Temperature Warning Light
highTire Pressure (TPMS) Light
mediumABS Warning Light
mediumBrake System Warning Light
highAirbag / SRS Warning Light
highTraction / Stability Control Light
lowPower Steering Warning Light
mediumTransmission Temperature Light
highGlow Plug Light (Diesel)
lowDiesel Particulate Filter (DPF) Light
mediumLow Fuel Light
lowLow Washer Fluid Light
lowSeat Belt Reminder Light
lowMaintenance Required / Service Light
lowReduced Engine Power / Limp Mode
highSecurity / Immobilizer Light
low

Misfire codes

P0300
Random/Multiple Cylinder Misfire DetectedP0301
Cylinder 1 Misfire DetectedP0302
Cylinder 2 Misfire DetectedP0303
Cylinder 3 Misfire DetectedP0304
Cylinder 4 Misfire DetectedP0305
Cylinder 5 Misfire DetectedP0306
Cylinder 6 Misfire DetectedP0307
Cylinder 7 Misfire DetectedP0308
Cylinder 8 Misfire Detected

Fuel & air codes

P0171
System Too Lean (Bank 1)P0174
System Too Lean (Bank 2)P0172
System Too Rich (Bank 1)P0175
System Too Rich (Bank 2)P0087
Fuel Rail/System Pressure - Too LowP0191
Fuel Rail Pressure Sensor Circuit Range/PerformanceP0230
Fuel Pump Primary CircuitP0234
Turbocharger/Supercharger Overboost ConditionP0299
Turbocharger/Supercharger Underboost

Emissions, EVAP & catalyst

P0420
Catalyst System Efficiency Below Threshold (Bank 1)P0430
Catalyst System Efficiency Below Threshold (Bank 2)P0400
Exhaust Gas Recirculation FlowP0401
Exhaust Gas Recirculation Flow Insufficient DetectedP0402
Exhaust Gas Recirculation Flow Excessive DetectedP0404
Exhaust Gas Recirculation Circuit Range/PerformanceP0411
Secondary Air Injection System Incorrect Flow DetectedP0440
Evaporative Emission SystemP0441
Evaporative Emission System Incorrect Purge FlowP0442
Evaporative Emission System Leak Detected (Small Leak)P0443
Evaporative Emission System Purge Control Valve CircuitP0446
Evaporative Emission System Vent Control CircuitP0449
Evaporative Emission System Vent Valve/Solenoid CircuitP0451
Evaporative Emission System Pressure Sensor/Switch Range/PerformanceP0455
Evaporative Emission System Leak Detected (Large Leak)P0456
Evaporative Emission System Leak Detected (Very Small Leak)P0457
Evaporative Emission System Leak Detected (Fuel Cap Loose/Off)P0496
Evaporative Emission System High Purge Flow

Sensor & timing codes

P0100
Mass or Volume Air Flow CircuitP0101
Mass or Volume Air Flow Circuit Range/PerformanceP0102
Mass or Volume Air Flow Circuit Low InputP0103
Mass or Volume Air Flow Circuit High InputP0068
MAP/MAF - Throttle Position CorrelationP0106
Manifold Absolute Pressure/Barometric Pressure Circuit Range/PerformanceP0107
Manifold Absolute Pressure/Barometric Pressure Circuit Low InputP0108
Manifold Absolute Pressure/Barometric Pressure Circuit High InputP0110
Intake Air Temperature Sensor 1 CircuitP0113
Intake Air Temperature Sensor 1 Circuit HighP0115
Engine Coolant Temperature CircuitP0117
Engine Coolant Temperature Circuit LowP0118
Engine Coolant Temperature Circuit HighP0120
Throttle/Pedal Position Sensor/Switch A CircuitP0121
Throttle/Pedal Position Sensor/Switch A Circuit Range/PerformanceP0122
Throttle/Pedal Position Sensor/Switch A Circuit LowP0125
Insufficient Coolant Temperature for Closed Loop Fuel ControlP0128
Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)P0130
O2 Sensor Circuit (Bank 1 Sensor 1)P0133
O2 Sensor Circuit Slow Response (Bank 1 Sensor 1)P0134
O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 1)P0135
O2 Sensor Heater Circuit (Bank 1 Sensor 1)P0136
O2 Sensor Circuit (Bank 1 Sensor 2)P0137
O2 Sensor Circuit Low Voltage (Bank 1 Sensor 2)P0138
O2 Sensor Circuit High Voltage (Bank 1 Sensor 2)P0141
O2 Sensor Heater Circuit (Bank 1 Sensor 2)P0155
O2 Sensor Heater Circuit (Bank 2 Sensor 1)P0161
O2 Sensor Heater Circuit (Bank 2 Sensor 2)P0217
Engine Coolant Over Temperature ConditionP0325
Knock Sensor 1 Circuit (Bank 1 or Single Sensor)P0335
Crankshaft Position Sensor A CircuitP0340
Camshaft Position Sensor A Circuit (Bank 1 or Single Sensor)P0016
Crankshaft Position - Camshaft Position Correlation (Bank 1 Sensor A)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)P0351
Ignition Coil "A" Primary/Secondary CircuitP0500
Vehicle Speed Sensor "A"P0562
System Voltage LowP0563
System Voltage HighP0571
Brake Switch "A" Circuit

Idle, computer & transmission

P0505
Idle Air Control SystemP0506
Idle Air Control System RPM Lower Than ExpectedP0507
Idle Air Control System RPM Higher Than ExpectedP0600
Serial Communication LinkP0606
Control Module ProcessorP0700
Transmission Control System (MIL Request)P0715
Input/Turbine Speed Sensor "A" CircuitP0730
Incorrect Gear RatioP0741
Torque Converter Clutch Circuit Performance or Stuck OffP0750
Shift Solenoid "A"