Common OBD2 trouble codes explained

When the check engine light comes on, an OBD2 scanner reads a code that points to the system with a problem. Here's what the most common codes mean, what usually causes them, and how to check them before buying parts.

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• P0010: A Camshaft Position Actuator Circuit (Bank 1)
• P0011: Intake 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)
• P0018: Crankshaft Position - Camshaft Position Correlation (Bank 2 Sensor A)
• P0087: Fuel Rail/System Pressure - Too Low
• P0101: Mass Air Flow (MAF) Sensor Circuit Range/Performance
• P0102: Mass Air Flow (MAF) Sensor Circuit Low Input
• P0103: Mass Air Flow (MAF) Sensor A Circuit High
• P0106: MAP/Barometric Pressure Sensor Circuit Range/Performance
• P0113: Intake Air Temperature (IAT) Sensor 1 Circuit High
• P0115: Engine Coolant Temperature Circuit Malfunction
• P0116: Engine Coolant Temperature Sensor 1 Circuit Range/Performance
• P0117: Engine Coolant Temperature Sensor 1 Circuit Low
• P0118: Engine Coolant Temperature Sensor 1 Circuit High
• P0121: Throttle/Pedal Position Sensor/Switch A Circuit Range/Performance
• P0122: Throttle/Pedal Position Sensor A Circuit Low
• P0123: Throttle/Pedal Position Sensor/Switch A Circuit High
• P0125: Insufficient Coolant Temperature for Closed Loop Fuel Control
• P0128: Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)
• P0130: O2 Sensor Circuit Malfunction (Bank 1, Sensor 1)
• P0131: O2 Sensor Circuit Low Voltage (Bank 1, Sensor 1)
• P0132: O2 Sensor Circuit High Voltage (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 Malfunction (Bank 1, Sensor 1)
• P0136: O2 Sensor Circuit Malfunction (Bank 1, Sensor 2)
• P0137: O2 Sensor Circuit Low Voltage (Bank 1, Sensor 2)
• P0138: O2 Sensor Circuit High Voltage (Bank 1, Sensor 2)
• P0139: O2 Sensor Circuit Slow Response (Bank 1, Sensor 2)
• P0140: O2 Sensor Circuit No Activity Detected (Bank 1, Sensor 2)
• P0141: O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 2)
• P0155: O2 Sensor Heater Circuit Malfunction (Bank 2, Sensor 1)
• P0171: System Too Lean (Bank 1)
• P0172: System Too Rich (Bank 1)
• P0174: System Too Lean (Bank 2)
• P0175: System Too Rich (Bank 2)
• P0191: Fuel Rail Pressure Sensor A Circuit Range/Performance
• P0201: Injector Circuit/Open - Cylinder 1
• P0299: Turbocharger/Supercharger A Underboost Condition
• 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
• P0307: Cylinder 7 Misfire Detected
• P0308: Cylinder 8 Misfire Detected
• P0325: Knock Sensor 1 Circuit Malfunction (Bank 1 or Single Sensor)
• P0327: Knock Sensor 1 Circuit Low (Bank 1 or Single Sensor)
• P0335: Crankshaft Position Sensor A Circuit Malfunction
• P0340: Camshaft Position Sensor A Circuit Malfunction (Bank 1 or Single Sensor)
• P0341: Camshaft Position Sensor A Circuit Range/Performance (Bank 1 or Single Sensor)
• P0351: Ignition Coil A Primary/Secondary Circuit
• P0401: Exhaust Gas Recirculation (EGR) Flow Insufficient Detected
• P0402: Exhaust Gas Recirculation (EGR) Flow Excessive Detected
• P0404: Exhaust Gas Recirculation Circuit Range/Performance
• P0410: Secondary Air Injection System
• P0420: Catalyst System Efficiency Below Threshold (Bank 1)
• P0430: Catalyst System Efficiency Below Threshold (Bank 2)
• P0440: Evaporative Emission System Malfunction
• P0441: Evaporative Emission System Incorrect Purge Flow
• P0442: Evaporative Emission System Leak Detected (Small Leak)
• P0443: Evaporative Emission System Purge Control Valve Circuit
• P0446: Evaporative Emission System Vent Control Circuit
• P0449: Evaporative Emission System Vent Valve/Solenoid Circuit
• P0452: Evaporative Emission System Pressure Sensor/Switch Low
• P0455: EVAP System Large Leak Detected
• 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
• P0500: Vehicle Speed Sensor A Malfunction
• P0501: Vehicle Speed Sensor A Range/Performance
• P0505: Idle Air Control System
• P0506: Idle Air Control System RPM Lower Than Expected
• P0507: Idle Air Control System RPM Higher Than Expected
• P0562: System Voltage Low
• P0700: Transmission Control System Malfunction
• P0705: Transmission Range Sensor Circuit Malfunction (PRNDL Input)
• P0715: Input/Turbine Speed Sensor A Circuit
• P0720: Output Speed Sensor Circuit Malfunction
• P0730: Incorrect Gear Ratio
• P0740: Torque Converter Clutch Circuit Malfunction
• P0741: Torque Converter Clutch Circuit Performance or Stuck Off
• P2135: Throttle/Pedal Position Sensor/Switch A/B Voltage Correlation
• P2187: System Too Lean at Idle (Bank 1)
• U0100: Lost Communication With ECM/PCM A

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