OBD-II car trouble codes
Since 1996 in the US and 2001–2004 in Europe, cars expose diagnostic trouble codes (DTCs) through the OBD-II port under the dashboard. A code such as P0420 means the engine computer saw a reading outside its expected range and usually switched on the check-engine light.
Each page explains what the code means, how serious it is and the common causes to test before replacing parts. A cheap OBD-II reader is enough to read and clear the codes.
60 codes · showing 1–60 · most-searched codes first
P0102AUTOMass or Volume Air Flow Circuit Low Input P0113AUTOIntake Air Temperature Sensor 1 Circuit High P0125AUTOInsufficient Coolant Temperature for Closed Loop Fuel Control P0137AUTOO2 Sensor Circuit Low Voltage (Bank 1, Sensor 2) P0300AUTORandom/Multiple Cylinder Misfire Detected P0301AUTOCylinder 1 Misfire Detected P0302AUTOCylinder 2 Misfire Detected P0303AUTOCylinder 3 Misfire Detected P0304AUTOCylinder 4 Misfire Detected P0305AUTOCylinder 5 Misfire Detected P0306AUTOCylinder 6 Misfire Detected P0325AUTOKnock Sensor 1 Circuit Malfunction (Bank 1 or Single Sensor) P0335AUTOCrankshaft Position Sensor A Circuit Malfunction P0341AUTOCamshaft Position Sensor A Circuit Range/Performance (Bank 1 or Single Sensor) P0401AUTOExhaust Gas Recirculation (EGR) Flow Insufficient Detected P0420AUTOCatalyst System Efficiency Below Threshold (Bank 1) P0430AUTOCatalyst System Efficiency Below Threshold (Bank 2) P0440AUTOEvaporative Emission Control System Malfunction P0442AUTOEvaporative Emission Control System Leak Detected (Small Leak) P0446AUTOEvaporative Emission Control System Vent Control Circuit Malfunction P0455AUTOEvaporative Emission Control System Leak Detected (Large Leak) P0456AUTOEvaporative Emission Control System Leak Detected (Very Small Leak) P0030AUTOThe engine control module has detected a problem with the heater circuit for the upstream oxygen sensor on… P0056AUTOThe engine control module has detected a problem with the heater circuit for the downstream oxygen sensor on… P0100AUTOThe engine control module is telling you that the signal from the Mass Air Flow sensor is out of the… P0103AUTOThe engine control module is seeing a voltage signal from the mass‑air‑flow sensor that is higher than the… P0106AUTOThe engine control module (ECM) is seeing a voltage signal from the MAP (Manifold Absolute Pressure) sensor… P0107AUTOThe engine control module is seeing a voltage that is lower than the minimum it expects from the MAP… P0110AUTOThe engine control module is telling you that the signal from the intake‑air‑temperature sensor is out of… P0122AUTOThe engine control module (ECM) sees a voltage that is too low from the Throttle Position Sensor (TPS) “A”… P0131AUTOThe engine control module sees a voltage that is too low from the upstream oxygen sensor on bank 1. This… P0138AUTOThe engine control module is seeing a voltage that is too high from the downstream oxygen sensor on bank 1… P0157AUTOThe engine control module detects a voltage that is too low from the downstream oxygen sensor on bank 2… P0158AUTOThe engine control module sees an unusually high voltage from the downstream oxygen sensor on bank 2 (the… P0161AUTOThe engine control module detects a problem in the heater circuit for the downstream oxygen sensor on bank… P0307AUTOThe engine control module has noticed that cylinder 7 is not completing its combustion cycle properly. This… P0308AUTOThe engine control module has detected that cylinder 8 is not completing its combustion cycle correctly. The… P0330AUTOThe engine control module (ECM) has detected an abnormal signal or no signal from the knock sensor on bank… P0336AUTOThe engine control module sees a voltage signal from the crankshaft position sensor that is out of the… P0345AUTOThe ECM does not receive a valid voltage signal from Camshaft Position Sensor A on bank 2, preventing… P0352AUTOThe engine control module has detected a problem in the primary or secondary circuit of Ignition Coil B… P0353AUTOThe engine control module (ECM) has detected an abnormal voltage or resistance condition in the primary or… P0354AUTOThe engine control module detects an abnormal voltage or resistance in the primary or secondary winding of… P0400AUTOThe engine control module detects that the EGR system is not moving the correct amount of exhaust gases back… P0402AUTOThe engine control module (ECM) has detected that more exhaust gas is being recirculated than the system… P0410AUTOThe engine control module has detected that the secondary‑air injection (SAI) system is not delivering the… P0411AUTOThe engine control module (ECM) has detected that the secondary‑air injection (SAI) system is delivering too… P0441AUTOThe engine control module has detected that the EVAP purge valve is allowing too much fuel vapor into the… P0443AUTOThe engine control module has detected a problem with the electrical circuit that operates the EVAP purge… P0449AUTOThe engine control module has detected a problem with the vent valve or its control circuit in the… P0451AUTOThe engine control module has detected that the EVAP‑system pressure sensor is reporting values outside its… P0452AUTOThe engine control module has detected that the pressure sensor in the evaporative emission (EVAP) system is… P0496AUTOThe PCM has detected that the EVAP purge valve is allowing more vapor flow than expected during the purge… P1101AUTOThe engine control module has detected that the intake airflow system is not delivering the expected… P1457AUTOThe engine control module has sensed that the evaporative emissions (EVAP) control canister is leaking. Fuel… SYMPTOM-BLACK-SMOKEAUTOThe engine is delivering more fuel than air, creating a fuel‑rich mixture that burns incompletely. The… SYMPTOM-FAILED-EMISSIONSAUTOThe powertrain control module has determined that the vehicle did not meet the required emissions standards… SYMPTOM-HARD-STARTAUTOThe SYMPTOM-HARD-START code tells the powertrain control module that the engine needs more than normal… SYMPTOM-ROUGH-IDLEAUTOThe engine control module has detected irregular engine speed when the throttle is closed. In plain English… SYMPTOM-WONT-STARTAUTOThe SYMPTOM-WONT-START code appears when the powertrain control module detects that the engine fails to…