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

• P252A — Engine Oil Quality Sensor Circuit (P252A): 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, corroded, loose or damaged connector, blown fuse feeding the circuit.
• P252C — P252C — Engine Oil Quality Sensor Circuit Low. 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, blown fuse feeding the circuit.
• P252D — Engine Oil Quality Sensor Circuit High (P252D): 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, open or shorted wiring in the circuit, faulty sensor or actuator of the affected circuit.
• P252E — OBD2 code P252E flags a problem with the sensor and actuator circuits (engine oil quality circuit intermittent/erratic). The car is usually drivable while you plan the repair. Common culprits: faulty sensor or actuator of the affected circuit, open or shorted wiring in the circuit, poor ground connection.
• P252F — Engine Oil Level Too High (P252F): 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, open or shorted wiring in the circuit, control module driver fault.
• P2532 — P2532 — Ignition Switch Run Position Circuit High. A fault in the ignition system. Short, gentle driving to a shop is usually possible. Typical causes: worn spark plugs or wrong plug gap, damaged coil wiring or connector, moisture or oil in the spark plug wells.
• P2533 — Ignition Switch Run/Start Position Circuit (P2533): a powertrain (engine/transmission) fault affecting the ignition system. Short, gentle driving to a shop is usually possible. Most often caused by damaged coil wiring or connector, faulty ignition control circuit in the ECM, moisture or oil in the spark plug wells.
• P2534 — OBD2 code P2534 flags a problem with the ignition system (ignition switch run/start position circuit low). Short, gentle driving to a shop is usually possible. Common culprits: faulty ignition control circuit in the ECM, moisture or oil in the spark plug wells, worn spark plugs or wrong plug gap.
• P2535 — Ignition Switch Run/Start Position Circuit High (P2535): a powertrain (engine/transmission) fault affecting the ignition system. Short, gentle driving to a shop is usually possible. Most often caused by failed ignition coil or coil pack, moisture or oil in the spark plug wells, faulty ignition control circuit in the ECM.
• P2536 — OBD2 code P2536 flags a problem with the ignition system (ignition switch accessory position circuit). Short, gentle driving to a shop is usually possible. Common culprits: faulty ignition control circuit in the ECM, moisture or oil in the spark plug wells, damaged coil wiring or connector.
• P2537 — Ignition Switch Accessory Position Circuit Low (P2537): a powertrain (engine/transmission) fault affecting the ignition system. Short, gentle driving to a shop is usually possible. Most often caused by failed ignition coil or coil pack, damaged coil wiring or connector, moisture or oil in the spark plug wells.
• P2539 — P2539 — Low Pressure Fuel System Sensor Circuit. A fault in the fuel delivery and mixture control. Short, gentle driving to a shop is usually possible. Typical causes: weak fuel pump or clogged fuel filter, faulty fuel rail pressure sensor or wiring, faulty fuel pressure regulator.
• P253A — PTO Sense Circuit/Open (P253A): 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.
• P253B — OBD2 code P253B flags a problem with the sensor and actuator circuits (PTO sense circuit range/performance). The car is usually drivable while you plan the repair. Common culprits: control module driver fault, blown fuse feeding the circuit, open or shorted wiring in the circuit.
• P253C — P253C — PTO Sense Circuit Low. 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, blown fuse feeding the circuit.
• P253D — OBD2 code P253D flags a problem with the sensor and actuator circuits (PTO sense circuit high). The car is usually drivable while you plan the repair. Common culprits: open or shorted wiring in the circuit, blown fuse feeding the circuit, faulty sensor or actuator of the affected circuit.
• P253E — PTO Sense Circuit Intermittent/Erratic (P253E): 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, control module driver fault, corroded, loose or damaged connector.
• P253F — Engine Oil Deteriorated (P253F): 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, control module driver fault, blown fuse feeding the circuit.
• P2540 — OBD2 code P2540 flags a problem with the fuel delivery and mixture control (low pressure fuel system sensor circuit range/performance). Short, gentle driving to a shop is usually possible. Common culprits: faulty fuel pressure regulator, clogged or leaking fuel injectors, faulty fuel rail pressure sensor or wiring.
• P2543 — Low Pressure Fuel System Sensor Circuit Intermittent (P2543): a powertrain (engine/transmission) fault affecting the fuel delivery and mixture control. Short, gentle driving to a shop is usually possible. Most often caused by contaminated or incorrect fuel, weak fuel pump or clogged fuel filter, vacuum or intake leaks skewing the mixture.
• P2545 — P2545 — Torque Management Request Input Signal "A" Range/Performance. A fault in the sensor and actuator circuits. The car is usually drivable while you plan the repair. Typical causes: control module driver fault, poor ground connection, faulty sensor or actuator of the affected circuit.
• P2546 — OBD2 code P2546 flags a problem with the sensor and actuator circuits (torque management request input signal "A" low). The car is usually drivable while you plan the repair. Common culprits: poor ground connection, corroded, loose or damaged connector, blown fuse feeding the circuit.
• P2547 — P2547 — Torque Management Request Input Signal "A" High. A fault in the sensor and actuator circuits. The car is usually drivable while you plan the repair. Typical causes: control module driver fault, poor ground connection, blown fuse feeding the circuit.
• P2548 — OBD2 code P2548 flags a problem with the sensor and actuator circuits (torque management request input signal "B"). The car is usually drivable while you plan the repair. Common culprits: blown fuse feeding the circuit, corroded, loose or damaged connector, poor ground connection.