P0300: Random or Multiple Cylinder Misfire
P0300 means the engine computer detected misfires that are not limited to one cylinder.
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OBD-II Code Guides
Trouble codes are clues, not final diagnoses. Use them with symptoms and test results.
P0171: System Too Lean Bank 1
P0171 means the engine computer is adding fuel because it sees too much air or not enough fuel on bank 1.
P0420: Catalyst System Efficiency Below Threshold
P0420 means the catalytic converter is not storing oxygen as expected, or the sensor data makes it appear that way.
P0455: Large EVAP System Leak Detected
P0455 means the evaporative emissions system cannot hold pressure or vacuum during a leak test.
P0128: Coolant Temperature Below Thermostat Regulating Temperature
P0128 usually means the engine is warming up too slowly or not reaching the expected operating temperature.
P0135: Oxygen Sensor Heater Circuit Bank 1 Sensor 1
P0135 means the upstream oxygen sensor heater circuit is not working as expected.
P0301: Cylinder 1 Misfire Detected
P0301 means the engine computer detected a misfire on cylinder 1.
P0302: Cylinder 2 Misfire Detected
P0302 means cylinder 2 is misfiring often enough for the computer to flag a fault.
P0303: Cylinder 3 Misfire Detected
P0303 indicates a misfire isolated to cylinder 3.
P0304: Cylinder 4 Misfire Detected
P0304 means the engine computer has detected misfire activity on cylinder 4.
P0174: System Too Lean Bank 2
P0174 means the engine computer is adding extra fuel because bank 2 is running lean.
P0430: Catalyst System Efficiency Below Threshold Bank 2
P0430 means the catalytic converter monitor for bank 2 is below the expected efficiency threshold.
P0440: EVAP System Malfunction
P0440 means the evaporative emissions system failed a general leak or flow test.
P0442: Small EVAP Leak Detected
P0442 means the EVAP system has a small leak, often too small to see without testing.
P0456: Very Small EVAP Leak Detected
P0456 points to a very small leak in the fuel vapor system.
P0101: Mass Airflow Sensor Range or Performance
P0101 means the MAF sensor reading is outside the range the computer expects.
P0113: Intake Air Temperature Sensor Circuit High
P0113 means the intake air temperature signal is higher than expected electrically, often indicating an open circuit.
P0118: Engine Coolant Temperature Sensor Circuit High
P0118 means the coolant temperature sensor circuit is reading out of range, often as extremely cold.
P0507: Idle Control System RPM Higher Than Expected
P0507 means idle speed is higher than the computer expects.
P0700: Transmission Control System Malfunction
P0700 means the transmission control module has requested the engine computer to turn on the warning light.
P0740: Torque Converter Clutch Circuit Malfunction
P0740 means the torque converter clutch control circuit or operation is not behaving as expected.
P0172: System Too Rich Bank 1
P0172 means the engine computer is removing fuel because bank 1 appears to be running too rich.
P0102: Mass Airflow Circuit Low Input
P0102 means the mass airflow sensor signal is lower than expected.
P0441: EVAP Incorrect Purge Flow
P0441 means purge flow through the EVAP system is not what the computer expected.
P0443: EVAP Purge Control Valve Circuit
P0443 means the electrical circuit for the purge control valve has a fault.
P0496: EVAP Flow During Non-Purge
P0496 means fuel vapor is flowing when the EVAP purge system should be closed.
P0325: Knock Sensor Circuit Malfunction
P0325 means the engine computer detected a problem in the knock sensor circuit.
P0520: Engine Oil Pressure Sensor Circuit
P0520 means the oil pressure sensor or circuit signal is not believable to the engine computer.
P0521: Engine Oil Pressure Sensor Range or Performance
P0521 means the oil pressure sensor signal is outside the expected range for engine conditions.
P0401: Exhaust Gas Recirculation Flow Insufficient
P0401 means the EGR system is not flowing as much exhaust gas as expected.
P0402: Exhaust Gas Recirculation Flow Excessive
P0402 means the EGR system appears to be flowing too much exhaust gas.
P0404: EGR Circuit Range or Performance
P0404 means the EGR position or control signal is not matching what the computer expects.
P0505: Idle Control System Malfunction
P0505 means the engine computer cannot control idle speed as expected.
P0121: Throttle Position Sensor Range or Performance
P0121 means the throttle position signal does not match expected range or behavior.
P0122: Throttle Position Sensor Circuit Low
P0122 means the throttle position sensor signal is lower than expected.
P0201: Injector Circuit Cylinder 1
P0201 means the fuel injector circuit for cylinder 1 has an electrical fault.
P0202: Injector Circuit Cylinder 2
P0202 means the fuel injector circuit for cylinder 2 has an electrical fault.
P0203: Injector Circuit Cylinder 3
P0203 means the fuel injector circuit for cylinder 3 has an electrical fault.
P0204: Injector Circuit Cylinder 4
P0204 means the fuel injector circuit for cylinder 4 has an electrical fault.
P0130: Oxygen Sensor Circuit Bank 1 Sensor 1
P0130 means the upstream oxygen sensor circuit on bank 1 is not behaving as expected.
P0141: Oxygen Sensor Heater Circuit Bank 1 Sensor 2
P0141 means the downstream oxygen sensor heater circuit on bank 1 has a fault.
P0155: Oxygen Sensor Heater Circuit Bank 2 Sensor 1
P0155 means the upstream oxygen sensor heater circuit on bank 2 has a fault.
P0305: Cylinder 5 Misfire Detected
P0305 means the engine computer detected a misfire on cylinder 5.
P0306: Cylinder 6 Misfire Detected
P0306 means the engine computer detected a misfire on cylinder 6.
P0705: Transmission Range Sensor Circuit
P0705 means the transmission range sensor signal is missing, inconsistent, or out of expected range.