All OBD2 Diagnostic Codes
Browse our complete database of 16000 diagnostic trouble codes.
P0400: Emissions Control System Malfunction
The engine control module (ECM) has detected that the emissions control system is not operating within normal parameters, which can cause increased emissions and potentially harm the environment.
Exhaust Gas Recirculation Flow Insufficient Detected
The EGR system is not flowing enough exhaust gas back into the intake to reduce NOx emissions. This is one of the most common emission-related codes.
Exhaust Gas Recirculation Flow Excessive Detected
The EGR system is flowing too much exhaust gas back into the intake, causing performance issues.
P0403: Emissions Control System Not Operating Within Normal Parameters
The Emissions Control System is not functioning within normal parameters, which can cause increased emissions and potentially fail emissions tests.
Exhaust Gas Recirculation Circuit Range/Performance
The EGR valve position does not match what the engine control module expects based on operating conditions.
P0405: Emissions Control System Not Operating Within Normal Parameters
The engine control module (ECM) has detected that the emissions control system is not operating within normal parameters, which can cause increased emissions and potentially harm the environment.
P0406: Emissions Control System Not Operating Within Normal Parameters
The engine control module (ECM) has detected that the emissions control system is not operating within normal parameters, which can cause increased emissions and potentially harm the environment.
P0407: Emissions Control System Not Operating Within Normal Parameters
The engine control module (ECM) has detected that the emissions control system is not operating within normal parameters, which can cause increased emissions and potentially harm the environment.
P0408: Emissions Control System Not Operating Within Normal Parameters
The engine control module (ECM) has detected that the emissions control system is not operating within normal parameters, which can cause increased emissions and potentially harm the environment.
P0409: Emissions Control System Not Operating Within Normal Parameters
The engine control module (ECM) has detected that the emissions control system is not operating within normal parameters, which can cause increased emissions and potentially harm the environment.
P0410: Emissions Control System Not Operating Within Normal Parameters
The engine control module (ECM) has detected that the emissions control system is not operating within normal parameters, which can cause the vehicle to fail emissions tests and potentially lead to decreased fuel efficiency and increased emissions.
Secondary Air Injection System Incorrect Flow Detected
The secondary air injection system is not providing the correct airflow to reduce emissions during cold start.
Secondary Air Injection System Switching Valve A Circuit Malfunction
The switching valve that controls secondary air injection flow has an electrical malfunction.
Secondary Air Injection System Switching Valve A Circuit Open
The switching valve circuit for secondary air injection has an open circuit preventing operation.
Secondary Air Injection System Switching Valve A Circuit Shorted
The switching valve circuit for secondary air injection has a short circuit.
P0415: Emissions Control System Not Operating Within Normal Parameters
The engine control module (ECM) has detected that the emissions control system is not operating within normal parameters, which can cause increased emissions and potentially affect the vehicle's performance.
P0416: Emissions Control System Not Operating Within Normal Parameters
The engine control module (ECM) has detected that the emissions control system is not operating within normal parameters, which can cause increased emissions and potentially harm the environment.
P0417: Emissions Control System Not Operating Within Normal Parameters
The engine control module (ECM) has detected that the emissions control system is not operating within normal parameters, which can cause increased emissions and potentially harm the environment.
P0418: Emissions Control System Not Operating Within Normal Parameters
The engine control module (ECM) has detected that the emissions control system is not operating within normal parameters, which can cause increased emissions and potentially harm the environment.
P0419: Emissions Control System Not Operating Within Normal Parameters
The engine control module (ECM) has detected that the emissions control system is not operating within normal parameters, which can cause increased emissions and potentially harm the environment.
Catalyst System Efficiency Below Threshold Bank 1
The catalytic converter on bank 1 is not operating efficiently. The oxygen sensors before and after the catalytic converter are showing similar readings, indicating the catalyst is not properly cleaning the exhaust gases.
P0421: Catalytic Converter Efficiency Below Threshold
The catalytic converter is not functioning within normal parameters, which can cause excessive emissions and decreased fuel efficiency.
P0422: Catalyst Efficiency Below Threshold
The onboard computer has detected that the catalytic converter is not functioning within normal parameters, which can cause excessive emissions and decreased fuel efficiency.
P0423: Catalyst Efficiency Below Threshold
The onboard computer has detected that the catalytic converter is not functioning within normal parameters, which can cause excessive emissions and decreased fuel efficiency.
P0424: Catalyst Efficiency Below Threshold
The onboard computer has detected that the catalytic converter is not functioning within normal parameters, which can lead to increased emissions and decreased fuel efficiency.
P0425: Catalytic Converter Efficiency Below Threshold
The catalytic converter is not functioning within normal parameters, which can cause excessive emissions and decreased fuel efficiency.
P0426: Catalyst Efficiency Below Threshold
The onboard computer has detected that the catalytic converter is not functioning within normal parameters, which can lead to increased emissions and decreased fuel efficiency.
P0427: Catalytic Converter Efficiency Below Threshold
The catalytic converter is not functioning within normal parameters, which can cause excessive emissions and decreased fuel efficiency.
P0428: Catalytic Converter Efficiency Below Threshold
The catalytic converter is not functioning within normal parameters, which can cause excessive emissions and decreased fuel efficiency.
P0429: Catalyst Efficiency Below Threshold
The onboard computer has detected that the catalytic converter is not functioning within normal parameters, which can lead to increased emissions and decreased fuel efficiency.
Catalyst System Efficiency Below Threshold Bank 2
The catalytic converter on bank 2 is not operating efficiently. Similar to P0420 but affects the second bank of cylinders in V6/V8 engines.
P0431: Exhaust Gas Recirculation (EGR) System Malfunction
The EGR system is not operating within normal parameters, which can cause increased emissions and decreased engine performance.
P0432: Emissions Control System Not Operating Within Normal Parameters
The engine's emissions control system is not functioning within normal parameters, which can cause increased emissions and potentially harm the environment.
P0433: Emissions Control System Not Operating Within Normal Parameters
The engine's emissions control system is not functioning within normal parameters, which can cause increased emissions and potentially harm the environment.
P0434: Emissions Control System Not Operating Within Normal Parameters
The engine's emissions control system is not functioning within normal parameters, which can cause increased emissions and potentially harm the environment.
P0435: Emissions Control System Not Operating Within Normal Parameters
The engine's emissions control system is not functioning within normal parameters, which can cause increased emissions and potentially harm the environment.
P0436: Emissions Control System Not Operating Within Normal Parameters
The engine's emissions control system is not functioning within normal parameters, which can cause increased emissions and potentially harm the environment.
P0437: Emissions Control System Not Operating Within Normal Parameters
The engine's emissions control system is not functioning within normal parameters, which can cause increased emissions and potentially harm the environment.
P0438: Emissions Control System Not Operating Within Normal Parameters
The engine's emissions control system is not functioning within normal parameters, which can cause increased emissions and potentially harm the environment.
P0439: Emissions Control System Not Operating Within Normal Parameters
The engine's emissions control system is not functioning within normal parameters, which can cause increased emissions and potentially harm the environment.
Evaporative Emission Control System Malfunction
General malfunction detected in the EVAP system that prevents fuel vapors from escaping to atmosphere.
P0441: Evaporative Emission Control System Malfunction
The Evaporative Emission Control System (EVAP) is not functioning properly, which can cause fuel vapors to escape into the atmosphere instead of being recycled back into the engine.
EVAP System Leak Detected Small Leak
A small leak has been detected in the evaporative emission control system. This system prevents fuel vapors from escaping into the atmosphere.
Evaporative Emission Control System Purge Control Valve Circuit Malfunction
The EVAP purge valve that controls fuel vapor flow from the charcoal canister has an electrical problem.
Evaporative Emission Control System Purge Control Valve Circuit Open
The EVAP purge valve circuit has an open circuit preventing proper valve operation.
Evaporative Emission Control System Purge Control Valve Circuit Shorted
The EVAP purge valve circuit has a short circuit that may damage the valve or control module.
Evaporative Emission Control System Vent Control Circuit Malfunction
The EVAP system vent valve is not operating properly, preventing proper venting of the fuel tank.
Evaporative Emission Control System Vent Control Circuit Open
The EVAP vent valve circuit has an open circuit preventing proper fuel tank venting.
Evaporative Emission Control System Vent Control Circuit Shorted
The EVAP vent valve circuit has a short circuit that may damage components.
Evaporative Emission Control System Vent Valve/Solenoid Circuit Malfunction
The EVAP vent valve or solenoid has a general electrical malfunction affecting its operation.