OBD2 Fault Code Library

Free lookup for thousands of OBD2 trouble codes: filter by family, read short meanings, and open deeper articles. Desktop ELM327 scanner with live data and AI guidance.

OBD2 symptoms

Look up diagnostic trouble codes by what the car is doing: misfire, overheating, rough idle, a check engine light, and other common symptoms.

• Engine misfire
• Engine overheating
• Rough idle
• Check engine light
• Poor fuel economy
• Hard starting
• Engine stalling
• Catalytic converter efficiency
• Oxygen sensor fault
• EVAP leak
• Thermostat not reaching temperature
• Lean air-fuel mixture
• Rich air-fuel mixture
• EGR flow fault
• Engine knock
• Charging system
• Throttle position
• Mass airflow sensor
• Turbo underboost
• Coolant temperature sensor
• Transmission fault

• P0496 — OBD2 code P0496 flags a problem with the evaporative emission (EVAP) system (EVAP flow during a non-purge condition). The car is usually drivable while you plan the repair. Common culprits: small leak in the fuel tank or filler neck, loose, damaged or wrong fuel cap, faulty purge valve (canister purge solenoid).
• P0497 — OBD2 code P0497 flags a problem with the evaporative emission (EVAP) system (evaporative emission system low purge flow). The car is usually drivable while you plan the repair. Common culprits: faulty purge valve (canister purge solenoid), loose, damaged or wrong fuel cap, faulty vent valve or leak detection pump.
• P0498 — OBD2 code P0498 flags a problem with the evaporative emission (EVAP) system (evaporative emission system vent valve control circuit low). The car is usually drivable while you plan the repair. Common culprits: loose, damaged or wrong fuel cap, saturated or damaged charcoal canister, faulty purge valve (canister purge solenoid).
• P0499 — P0499 — Evaporative Emission System Vent Valve Control Circuit High. A fault in the evaporative emission (EVAP) system. The car is usually drivable while you plan the repair. Typical causes: small leak in the fuel tank or filler neck, saturated or damaged charcoal canister, faulty purge valve (canister purge solenoid).
• P049A — OBD2 code P049A flags a problem with the exhaust gas recirculation (EGR) system (exhaust gas recirculation "B" flow). The car is usually drivable while you plan the repair. Common culprits: vacuum leaks in EGR control lines, carbon buildup blocking the EGR valve or passages, ECM control circuit fault.
• P049B — OBD2 code P049B flags a problem with the exhaust gas recirculation (EGR) system (exhaust gas recirculation "B" flow insufficient detected). The car is usually drivable while you plan the repair. Common culprits: ECM control circuit fault, failed EGR valve or position sensor, carbon buildup blocking the EGR valve or passages.
• P049C — P049C — Exhaust Gas Recirculation "B" Flow Excessive Detected. A fault in the exhaust gas recirculation (EGR) system. The car is usually drivable while you plan the repair. Typical causes: failed EGR valve or position sensor, carbon buildup blocking the EGR valve or passages, faulty EGR solenoid or wiring.
• P049D — OBD2 code P049D flags a problem with the exhaust gas recirculation (EGR) system (exhaust gas recirculation "A" control position exceeded learning limit). The car is usually drivable while you plan the repair. Common culprits: failed EGR valve or position sensor, faulty EGR solenoid or wiring, ECM control circuit fault.
• P049E — OBD2 code P049E flags a problem with the exhaust gas recirculation (EGR) system (exhaust gas recirculation "B" control position exceeded learning limit). The car is usually drivable while you plan the repair. Common culprits: vacuum leaks in EGR control lines, faulty EGR solenoid or wiring, carbon buildup blocking the EGR valve or passages.
• P049F — Exhaust Pressure Control Valve "B" (P049F): a powertrain (engine/transmission) fault affecting the sensor and actuator circuits. The car is usually drivable while you plan the repair. Most often caused by corroded, loose or damaged connector, control module driver fault, faulty sensor or actuator of the affected circuit.
• P04A0 — OBD2 code P04A0 flags a problem with the sensor and actuator circuits (exhaust pressure control valve "B" range/performance). The car is usually drivable while you plan the repair. Common culprits: poor ground connection, corroded, loose or damaged connector, open or shorted wiring in the circuit.
• P04A1 — Exhaust Pressure Control Valve "B" Low (P04A1): a powertrain (engine/transmission) fault affecting the sensor and actuator circuits. The car is usually drivable while you plan the repair. Most often caused by poor ground connection, corroded, loose or damaged connector, open or shorted wiring in the circuit.
• P04A2 — OBD2 code P04A2 flags a problem with the sensor and actuator circuits (exhaust pressure control valve "B" high). The car is usually drivable while you plan the repair. Common culprits: blown fuse feeding the circuit, poor ground connection, corroded, loose or damaged connector.
• P04A3 — OBD2 code P04A3 flags a problem with the sensor and actuator circuits (exhaust pressure control valve " B" intermittent). The car is usually drivable while you plan the repair. Common culprits: open or shorted wiring in the circuit, poor ground connection, faulty sensor or actuator of the affected circuit.
• P04A4 — Exhaust Pressure Control Valve "B" Stuck Open (P04A4): a powertrain (engine/transmission) fault affecting the sensor and actuator circuits. The car is usually drivable while you plan the repair. Most often caused by blown fuse feeding the circuit, poor ground connection, corroded, loose or damaged connector.
• P04A5 — P04A5 — Exhaust Pressure Control Valve "B" Stuck Closed. A fault in the sensor and actuator circuits. The car is usually drivable while you plan the repair. Typical causes: blown fuse feeding the circuit, poor ground connection, faulty sensor or actuator of the affected circuit.
• P04A6 — P04A6 — Exhaust Pressure Control Valve "B" Position Sensor/Switch Circuit. A fault in the sensor and actuator circuits. The car is usually drivable while you plan the repair. Typical causes: open or shorted wiring in the circuit, faulty sensor or actuator of the affected circuit, poor ground connection.
• P04A7 — OBD2 code P04A7 flags a problem with the sensor and actuator circuits (exhaust pressure control valve "B" position sensor/switch circuit range/performance). The car is usually drivable while you plan the repair. Common culprits: poor ground connection, blown fuse feeding the circuit, faulty sensor or actuator of the affected circuit.
• P04A8 — OBD2 code P04A8 flags a problem with the sensor and actuator circuits (exhaust pressure control valve "B" position sensor/switch circuit low). The car is usually drivable while you plan the repair. Common culprits: corroded, loose or damaged connector, control module driver fault, poor ground connection.
• P04A9 — OBD2 code P04A9 flags a problem with the sensor and actuator circuits (exhaust pressure control valve "B" position sensor/switch circuit high). The car is usually drivable while you plan the repair. Common culprits: blown fuse feeding the circuit, corroded, loose or damaged connector, control module driver fault.
• P04AA — P04AA — Exhaust Pressure Control Valve "B" Position Sensor/Switch Circuit Intermittent/Erratic. A fault in the sensor and actuator circuits. The car is usually drivable while you plan the repair. Typical causes: poor ground connection, open or shorted wiring in the circuit, corroded, loose or damaged connector.
• P0500 — OBD2 code P0500 flags a problem with the sensor and actuator circuits (vehicle speed sensor "A" malfunction). The car is usually drivable while you plan the repair. Common culprits: poor ground connection, open or shorted wiring in the circuit, faulty sensor or actuator of the affected circuit.
• P0501 — Vehicle Speed Sensor "A" Range/Performance (P0501): a powertrain (engine/transmission) fault affecting the sensor and actuator circuits. The car is usually drivable while you plan the repair. Most often caused by corroded, loose or damaged connector, blown fuse feeding the circuit, control module driver fault.
• P0502 — P0502 — Vehicle Speed Sensor "A" Low Input. A fault in the sensor and actuator circuits. The car is usually drivable while you plan the repair. Typical causes: blown fuse feeding the circuit, poor ground connection, corroded, loose or damaged connector.