Diagnostic library

Find an OBD2 code

Search the code from your scanner, then narrow the library by system, severity, or code family.

9,253 diagnostic guides

Sort

Find codes by symptomChoose what you notice to search matching code guides.

Rough idle or shakingVibration while stopped Hard to startLong cranking or no-start Engine stallsCuts out at idle or on the road Hesitates or loses powerSlow response when accelerating Battery light is onCharging system warning Harsh gear changesDelayed or rough shifting

A symptom can have several causes. Treat matching codes as clues and follow the diagnostic checks in each guide.

Emissions System Clear all

Quick browse

Choose a vehicle system

Engine1049 Emissions515 Fuel1016 Sensors & Electronics2110 Transmission866 Electrical & Charging1797 Body & Restraints193 Chassis & Brakes479 Network & Communication1228

FiltersSeverity · family

Severity

All severities9253 Low priority305 Check soon8256 Urgent621

Code family

All families9253 P · Powertrain7353 B · Body193 C · Chassis479 U · Network1228

Vehicle coverage

These are generic OBD2 definitions. Exact make, model, engine, and year compatibility will appear after vehicle-fitment data is added.

Diagnostic codes

Showing 49–72 of 515

Most searched first

P0439Catalyst Heater Control Circuit/Open Bank 2Check soonEmissions System30–120 minutes for initial diagnosisP0439 relates to catalyst heater control circuit/open bank 2. Check the fault conditions and vehicle-specific procedure before replacing parts.P043ACatalyst Temperature Sensor Circuit Bank 2 Sensor 2Check soonEmissions System30–120 minutes for initial diagnosisP043A relates to catalyst temperature sensor circuit bank 2 sensor 2. Check the fault conditions and vehicle-specific procedure before replacing parts.P043BCatalyst Temperature Sensor Circuit Range/Performance Bank 2 Sensor 2Check soonEmissions System30–120 minutes for initial diagnosisP043B relates to catalyst temperature sensor circuit range/performance bank 2 sensor 2. Check the fault conditions and vehicle-specific procedure before replacing parts.P043CCatalyst Temperature Sensor Circuit Low Bank 2 Sensor 2Check soonEmissions System30–120 minutes for initial diagnosisP043C relates to catalyst temperature sensor circuit low bank 2 sensor 2. Check the fault conditions and vehicle-specific procedure before replacing parts.P043DCatalyst Temperature Sensor Circuit High Bank 2 Sensor 2Check soonEmissions System30–120 minutes for initial diagnosisP043D relates to catalyst temperature sensor circuit high bank 2 sensor 2. Check the fault conditions and vehicle-specific procedure before replacing parts.P043EEVAP System Leak Detection Reference Orifice Low FlowLow priorityEmissions System30–120 minutes for initial diagnosisP043E relates to evap system leak detection reference orifice low flow. Check the fault conditions and vehicle-specific procedure before replacing parts.P043FEVAP System Leak Detection Reference Orifice High FlowLow priorityEmissions System30–120 minutes for initial diagnosisP043F relates to evap system leak detection reference orifice high flow. Check the fault conditions and vehicle-specific procedure before replacing parts.P0440Evaporative Emission Control System MalfunctionEmissions SystemFix P0440 EVAP system code. Learn what triggers a general EVAP fault and how to track down the source.P0441Evaporative Emission System Incorrect Purge FlowLow priorityEmissions System30–90 minutes for initial diagnosisP0441 means Evaporative Emission System Incorrect Purge Flow. Learn the likely symptoms, common causes, and a safe diagnostic order before replacing parts.P0444Evaporative Emission Control System Purge Control Valve Circuit OpenLow priorityEmissions System30–120 minutes for initial diagnosisP0444 indicates a fault related to evaporative emission control system purge control valve circuit open. Learn the likely causes and a practical diagnostic order before replacing parts.P0445Evaporative Emission Control System Purge Control Valve Circuit ShortedLow priorityEmissions System30–120 minutes for initial diagnosisP0445 indicates a fault related to evaporative emission control system purge control valve circuit shorted. Learn the likely causes and a practical diagnostic order before replacing parts.P0447Evaporative Emission Control System Vent Control Circuit OpenLow priorityEmissions System30–120 minutes for initial diagnosisP0447 indicates a fault related to evaporative emission control system vent control circuit open. Learn the likely causes and a practical diagnostic order before replacing parts.P0448Evaporative Emission Control System Vent Control Circuit ShortedLow priorityEmissions System30–120 minutes for initial diagnosisP0448 indicates a fault related to evaporative emission control system vent control circuit shorted. Learn the likely causes and a practical diagnostic order before replacing parts.P044AEGR Sensor C CircuitCheck soonEmissions System30–120 minutes for initial diagnosisP044A relates to egr sensor c circuit. Check the fault conditions and vehicle-specific procedure before replacing parts.P044BEGR Sensor C Circuit Range/PerformanceCheck soonEmissions System30–120 minutes for initial diagnosisP044B relates to egr sensor c circuit range/performance. Check the fault conditions and vehicle-specific procedure before replacing parts.P044CEGR Sensor C Circuit LowCheck soonEmissions System30–120 minutes for initial diagnosisP044C relates to egr sensor c circuit low. Check the fault conditions and vehicle-specific procedure before replacing parts.P044DEGR Sensor C Circuit HighCheck soonEmissions System30–120 minutes for initial diagnosisP044D relates to egr sensor c circuit high. Check the fault conditions and vehicle-specific procedure before replacing parts.P044EEGR Sensor C Circuit Intermittent/ErraticCheck soonEmissions System30–120 minutes for initial diagnosisP044E relates to egr sensor c circuit intermittent/erratic. Check the fault conditions and vehicle-specific procedure before replacing parts.P0450Evaporative Emission Control System Pressure Sensor MalfunctionLow priorityEmissions System30–120 minutes for initial diagnosisP0450 indicates a fault related to evaporative emission control system pressure sensor malfunction. Learn the likely causes and a practical diagnostic order before replacing parts.P0453Evaporative Emission Control System Pressure Sensor High InputLow priorityEmissions System30–120 minutes for initial diagnosisP0453 indicates a fault related to evaporative emission control system pressure sensor high input. Learn the likely causes and a practical diagnostic order before replacing parts.P0454Evaporative Emission Control System Pressure Sensor IntermittentLow priorityEmissions System30–120 minutes for initial diagnosisP0454 indicates a fault related to evaporative emission control system pressure sensor intermittent. Learn the likely causes and a practical diagnostic order before replacing parts.P0456EVAP System Very Small Leak DetectedEmissions SystemFix P0456 very small EVAP leak code. Learn how to find tiny evaporative system leaks and common fixes.P0457EVAP System Leak Detected (Fuel Cap Loose/Off)Emissions SystemFix P0457 EVAP fuel cap code. Learn why a loose or worn gas cap triggers this code and how to fix it fast.P0458EVAP System Purge Control Valve A Circuit LowLow priorityEmissions System30–120 minutes for initial diagnosisP0458 relates to evap system purge control valve a circuit low. Check the fault conditions and vehicle-specific procedure before replacing parts.