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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.

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

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All severities9253 Low priority305 Check soon8256 Urgent621

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

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

Diagnostic codes

Showing 1–24 of 515

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P0420Catalyst System Efficiency Below ThresholdLow priorityEmissions System60–150 minutesDiagnose P0420 catalyst efficiency below threshold on Bank 1. Learn what O2 sensor data can show and what to check before replacing the catalytic converter.P0442EVAP System Small Leak DetectedLow priorityEmissions System30–120 minutesFix P0442 evaporative emission system leak. Learn common causes of small EVAP leaks and how to find them.P0455EVAP System Large Leak DetectedEmissions SystemDiagnose P0455 large EVAP leak code. Find out what causes large evaporative system leaks and how to repair.P00FEEVAP System Tank Vapor Line Restricted/BlockedLow priorityEmissions System30–120 minutes for initial diagnosisP00FE relates to evap system tank vapor line restricted/blocked. Check the fault conditions and vehicle-specific procedure before replacing parts.P0142Oxygen Sensor Circuit Bank 1 Sensor 3Check soonEmissions System45–120 minutes for initial diagnosisP0142 means Oxygen Sensor Circuit Bank 1 Sensor 3. Learn the likely symptoms, causes, safety implications, and a practical diagnostic order.P0159Oxygen Sensor Circuit Slow Response Bank 2 Sensor 2Check soonEmissions System45–120 minutes for initial diagnosisP0159 means Oxygen Sensor Circuit Slow Response Bank 2 Sensor 2. Learn the likely symptoms, causes, safety implications, and a practical diagnostic order.P017FEVAP System Leak Detection Pump Module Air Filter RestrictedLow priorityEmissions System30–120 minutes for initial diagnosisP017F relates to evap system leak detection pump module air filter restricted. Check the fault conditions and vehicle-specific procedure before replacing parts.P0400Exhaust Gas Recirculation Flow MalfunctionLow priorityEmissions System30–90 minutes for initial diagnosisP0400 means Exhaust Gas Recirculation Flow Malfunction. Learn the likely symptoms, common causes, and a safe diagnostic order before replacing parts.P0401EGR Insufficient Flow DetectedEmissions SystemFix P0401 EGR flow code. Learn about the exhaust gas recirculation system and how to restore proper flow.P0402EGR Excessive Flow Detected - Causes & FixesEmissions SystemDiagnose the P0402 excessive EGR flow code, including stuck valves, blocked passages, and how to test the system.P0407Exhaust Gas Recirculation Sensor B Circuit LowCheck soonEmissions System30–90 minutes for initial diagnosisP0407 means the EGR position sensor B signal is below the expected electrical range. Learn what to check before replacing parts.P0408Exhaust Gas Recirculation Sensor B Circuit HighCheck soonEmissions System30–90 minutes for initial diagnosisP0408 means the EGR position sensor B signal is above the expected electrical range. Learn what to check before replacing parts.P0409Exhaust Gas Recirculation Sensor A CircuitCheck soonEmissions System30–90 minutes for initial diagnosisP0409 indicates the control module detected a fault in the EGR position-sensor A circuit. Learn what to inspect before replacing parts.P040AEGR Temperature Sensor A CircuitCheck soonEmissions System30–120 minutes for initial diagnosisP040A relates to egr temperature sensor a circuit. Check the fault conditions and vehicle-specific procedure before replacing parts.P040BEGR Temperature Sensor A Circuit Range/PerformanceCheck soonEmissions System30–120 minutes for initial diagnosisP040B relates to egr temperature sensor a circuit range/performance. Check the fault conditions and vehicle-specific procedure before replacing parts.P040CEGR Temperature Sensor A Circuit LowCheck soonEmissions System30–120 minutes for initial diagnosisP040C relates to egr temperature sensor a circuit low. Check the fault conditions and vehicle-specific procedure before replacing parts.P040DEGR Temperature Sensor A Circuit HighCheck soonEmissions System30–120 minutes for initial diagnosisP040D relates to egr temperature sensor a circuit high. Check the fault conditions and vehicle-specific procedure before replacing parts.P040EEGR Temperature Sensor A Circuit Intermittent/ErraticCheck soonEmissions System30–120 minutes for initial diagnosisP040E relates to egr temperature sensor a circuit intermittent/erratic. Check the fault conditions and vehicle-specific procedure before replacing parts.P040FEGR Temperature Sensor A/B CorrelationCheck soonEmissions System30–120 minutes for initial diagnosisP040F relates to egr temperature sensor a/b correlation. Check the fault conditions and vehicle-specific procedure before replacing parts.P0411Secondary Air Injection System Incorrect Flow DetectedLow priorityEmissions System30–90 minutes for initial diagnosisP0411 means Secondary Air Injection System Incorrect Flow Detected. Learn the likely symptoms, common causes, and a safe diagnostic order before replacing parts.P041AEGR Temperature Sensor B CircuitCheck soonEmissions System30–120 minutes for initial diagnosisP041A relates to egr temperature sensor b circuit. Check the fault conditions and vehicle-specific procedure before replacing parts.P041BEGR Temperature Sensor B Circuit Range/PerformanceCheck soonEmissions System30–120 minutes for initial diagnosisP041B relates to egr temperature sensor b circuit range/performance. Check the fault conditions and vehicle-specific procedure before replacing parts.P041CEGR Temperature Sensor B Circuit LowCheck soonEmissions System30–120 minutes for initial diagnosisP041C relates to egr temperature sensor b circuit low. Check the fault conditions and vehicle-specific procedure before replacing parts.P041DEGR Temperature Sensor B Circuit HighCheck soonEmissions System30–120 minutes for initial diagnosisP041D relates to egr temperature sensor b circuit high. Check the fault conditions and vehicle-specific procedure before replacing parts.