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

• P2567 — OBD2 code P2567 flags a problem with the catalytic converter efficiency monitoring (direct ozone reduction catalyst temperature sensor circuit). The car is usually drivable while you plan the repair. Common culprits: aged or contaminated catalytic converter, faulty downstream or upstream oxygen sensor, engine misfires damaging the catalyst.
• P2568 — OBD2 code P2568 flags a problem with the catalytic converter efficiency monitoring (direct ozone reduction catalyst temperature sensor circuit range/performance). The car is usually drivable while you plan the repair. Common culprits: faulty downstream or upstream oxygen sensor, persistent rich or lean fuel mixture, exhaust leak ahead of the converter.
• P2569 — P2569 — Direct Ozone Reduction Catalyst Temperature Sensor Circuit Low. A fault in the catalytic converter efficiency monitoring. The car is usually drivable while you plan the repair. Typical causes: faulty downstream or upstream oxygen sensor, aged or contaminated catalytic converter, engine misfires damaging the catalyst.
• P256A — Engine Idle Speed Selector Sensor/Switch Circuit/Open (P256A): 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 open or shorted wiring in the circuit, poor ground connection, control module driver fault.
• P256C — OBD2 code P256C flags a problem with the sensor and actuator circuits (engine idle speed selector sensor/switch circuit low). The car is usually drivable while you plan the repair. Common culprits: poor ground connection, open or shorted wiring in the circuit, control module driver fault.
• P256E — OBD2 code P256E flags a problem with the sensor and actuator circuits (engine idle speed selector sensor/switch circuit intermittent/erratic). The car is usually drivable while you plan the repair. Common culprits: blown fuse feeding the circuit, poor ground connection, open or shorted wiring in the circuit.
• P256F — P256F — A/C Request "B" Circuit Range/Performance. 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, open or shorted wiring in the circuit, poor ground connection.
• P2570 — Direct Ozone Reduction Catalyst Temperature Sensor Circuit High (P2570): a powertrain (engine/transmission) fault affecting the catalytic converter efficiency monitoring. The car is usually drivable while you plan the repair. Most often caused by faulty downstream or upstream oxygen sensor, aged or contaminated catalytic converter, engine misfires damaging the catalyst.
• P2571 — P2571 — Direct Ozone Reduction Catalyst Temperature Sensor Circuit Intermittent/Erratic. A fault in the catalytic converter efficiency monitoring. The car is usually drivable while you plan the repair. Typical causes: engine misfires damaging the catalyst, exhaust leak ahead of the converter, aged or contaminated catalytic converter.
• P2572 — P2572 — Direct Ozone Reduction Catalyst Deterioration Sensor Circuit. A fault in the catalytic converter efficiency monitoring. The car is usually drivable while you plan the repair. Typical causes: exhaust leak ahead of the converter, faulty downstream or upstream oxygen sensor, engine misfires damaging the catalyst.
• P2573 — P2573 — Direct Ozone Reduction Catalyst Deterioration Sensor Circuit Range/Performance. A fault in the catalytic converter efficiency monitoring. The car is usually drivable while you plan the repair. Typical causes: oil or coolant entering the exhaust, engine misfires damaging the catalyst, exhaust leak ahead of the converter.
• P2574 — OBD2 code P2574 flags a problem with the catalytic converter efficiency monitoring (direct ozone reduction catalyst deterioration sensor circuit low). The car is usually drivable while you plan the repair. Common culprits: oil or coolant entering the exhaust, faulty downstream or upstream oxygen sensor, engine misfires damaging the catalyst.
• P2575 — OBD2 code P2575 flags a problem with the catalytic converter efficiency monitoring (direct ozone reduction catalyst deterioration sensor circuit high). The car is usually drivable while you plan the repair. Common culprits: engine misfires damaging the catalyst, aged or contaminated catalytic converter, persistent rich or lean fuel mixture.
• P2576 — P2576 — Direct Ozone Reduction Catalyst Deterioration Sensor Circuit Intermittent/Erratic. A fault in the catalytic converter efficiency monitoring. The car is usually drivable while you plan the repair. Typical causes: exhaust leak ahead of the converter, persistent rich or lean fuel mixture, aged or contaminated catalytic converter.
• P2577 — OBD2 code P2577 flags a problem with the catalytic converter efficiency monitoring (direct ozone reduction catalyst efficiency below threshold). The car is usually drivable while you plan the repair. Common culprits: faulty downstream or upstream oxygen sensor, aged or contaminated catalytic converter, persistent rich or lean fuel mixture.
• P2578 — Turbocharger Speed Sensor Circuit (P2578): a powertrain (engine/transmission) fault affecting the turbocharger / supercharger boost control. Short, gentle driving to a shop is usually possible. Most often caused by boost leak in intercooler piping or hoses, vacuum or actuator line damage, faulty boost pressure sensor.
• P2579 — Turbocharger Speed Sensor Circuit Range/Performance (P2579): a powertrain (engine/transmission) fault affecting the turbocharger / supercharger boost control. Short, gentle driving to a shop is usually possible. Most often caused by boost leak in intercooler piping or hoses, worn turbocharger, clogged intake or exhaust (DPF/cat).
• P257B — Vacuum Reservoir Control Circuit Low (P257B): 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, blown fuse feeding the circuit, faulty sensor or actuator of the affected circuit.
• P257C — OBD2 code P257C flags a problem with the sensor and actuator circuits (vacuum reservoir control circuit high). The car is usually drivable while you plan the repair. Common culprits: corroded, loose or damaged connector, open or shorted wiring in the circuit, faulty sensor or actuator of the affected circuit.
• P257D — P257D — Engine Hood Switch Circuit Range/Performance. 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, corroded, loose or damaged connector, control module driver fault.
• P257F — OBD2 code P257F flags a problem with the sensor and actuator circuits (engine hood switch circuit high). The car is usually drivable while you plan the repair. Common culprits: control module driver fault, open or shorted wiring in the circuit, corroded, loose or damaged connector.
• P2580 — OBD2 code P2580 flags a problem with the turbocharger / supercharger boost control (turbocharger speed sensor circuit low). Short, gentle driving to a shop is usually possible. Common culprits: clogged intake or exhaust (DPF/cat), vacuum or actuator line damage, stuck wastegate or faulty boost control solenoid.
• P2582 — Turbocharger Speed Sensor Circuit Intermittent (P2582): a powertrain (engine/transmission) fault affecting the turbocharger / supercharger boost control. Short, gentle driving to a shop is usually possible. Most often caused by clogged intake or exhaust (DPF/cat), boost leak in intercooler piping or hoses, worn turbocharger.
• P2583 — OBD2 code P2583 flags a problem with the sensor and actuator circuits (cruise control front distance range sensor single sensor or center). The car is usually drivable while you plan the repair. Common culprits: blown fuse feeding the circuit, poor ground connection, open or shorted wiring in the circuit.