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

• P0039 — OBD2 code P0039 flags a problem with the turbocharger / supercharger boost control (turbo/super charger bypass valve control circuit range/performance). Short, gentle driving to a shop is usually possible. Common culprits: faulty boost pressure sensor, stuck wastegate or faulty boost control solenoid, clogged intake or exhaust (DPF/cat).
• P003A — Turbocharger/Supercharger Boost Control "A" Position Exceeded Learning Limit (P003A): a powertrain (engine/transmission) fault affecting the turbocharger / supercharger boost control. Short, gentle driving to a shop is usually possible. Most often caused by vacuum or actuator line damage, faulty boost pressure sensor, worn turbocharger.
• P003B — Turbocharger/Supercharger Boost Control "B" Position Exceeded Learning Limit (P003B): a powertrain (engine/transmission) fault affecting the turbocharger / supercharger boost control. Short, gentle driving to a shop is usually possible. Most often caused by vacuum or actuator line damage, boost leak in intercooler piping or hoses, clogged intake or exhaust (DPF/cat).
• P003C — "A" Camshaft Profile Control Performance/Stuck Off Bank 1 (P003C): a powertrain (engine/transmission) fault affecting the camshaft position and variable valve timing. Short, gentle driving to a shop is usually possible. Most often caused by worn cam phaser, faulty camshaft position sensor, stuck or clogged VVT oil control valve (OCV).
• P003D — "A" Camshaft Profile Control Stuck On Bank 1 (P003D): a powertrain (engine/transmission) fault affecting the camshaft position and variable valve timing. Short, gentle driving to a shop is usually possible. Most often caused by worn timing chain/belt or jumped timing, worn cam phaser, stuck or clogged VVT oil control valve (OCV).
• P003E — OBD2 code P003E flags a problem with the camshaft position and variable valve timing ("A" camshaft profile control performance/stuck off bank 2). Short, gentle driving to a shop is usually possible. Common culprits: faulty camshaft position sensor, damaged sensor wiring or reluctor ring, worn cam phaser.
• P003F — "A" Camshaft Profile Control Stuck On Bank 2 (P003F): a powertrain (engine/transmission) fault affecting the camshaft position and variable valve timing. Short, gentle driving to a shop is usually possible. Most often caused by worn timing chain/belt or jumped timing, worn cam phaser, stuck or clogged VVT oil control valve (OCV).
• P0040 — OBD2 code P0040 flags a problem with the oxygen sensor circuit (upstream oxygen sensors swapped from bank to bank). The car is usually drivable while you plan the repair. Common culprits: exhaust leak near the sensor, damaged sensor wiring or connector, oil or coolant contamination of the sensor tip.
• P0041 — Downstream Oxygen Sensors Swapped From Bank To Bank (P0041): a powertrain (engine/transmission) fault affecting the oxygen sensor circuit. The car is usually drivable while you plan the repair. Most often caused by damaged sensor wiring or connector, exhaust leak near the sensor, ECM signal circuit fault.
• P0042 — OBD2 code P0042 flags a problem with the oxygen sensor circuit (HO2S heater control circuit (bank 1 sensor 3)). The car is usually drivable while you plan the repair. Common culprits: blown sensor heater fuse, oil or coolant contamination of the sensor tip, exhaust leak near the sensor.
• P0043 — HO2S Heater Control Circuit Low (Bank 1 Sensor 3) (P0043): a powertrain (engine/transmission) fault affecting the oxygen sensor circuit. The car is usually drivable while you plan the repair. Most often caused by ECM signal circuit fault, blown sensor heater fuse, aged or contaminated oxygen sensor.
• P0044 — OBD2 code P0044 flags a problem with the oxygen sensor circuit (HO2S heater control circuit high (bank 1 sensor 3)). The car is usually drivable while you plan the repair. Common culprits: exhaust leak near the sensor, blown sensor heater fuse, ECM signal circuit fault.
• P0045 — OBD2 code P0045 flags a problem with the turbocharger / supercharger boost control (turbocharger/supercharger boost control "A" circuit/open). Short, gentle driving to a shop is usually possible. Common culprits: vacuum or actuator line damage, clogged intake or exhaust (DPF/cat), worn turbocharger.
• P0046 — Turbocharger/Supercharger Boost Control "A" Circuit Range/Performance (P0046): a powertrain (engine/transmission) fault affecting the turbocharger / supercharger boost control. Short, gentle driving to a shop is usually possible. Most often caused by stuck wastegate or faulty boost control solenoid, worn turbocharger, vacuum or actuator line damage.
• P0047 — P0047 — Turbocharger/Supercharger Boost Control "A" Circuit Low. A fault in the turbocharger / supercharger boost control. Short, gentle driving to a shop is usually possible. Typical causes: worn turbocharger, vacuum or actuator line damage, stuck wastegate or faulty boost control solenoid.
• P0048 — Turbocharger/Supercharger Boost Control "A" Circuit High (P0048): a powertrain (engine/transmission) fault affecting the turbocharger / supercharger boost control. Short, gentle driving to a shop is usually possible. Most often caused by vacuum or actuator line damage, clogged intake or exhaust (DPF/cat), boost leak in intercooler piping or hoses.
• P0049 — Turbocharger/Supercharger Turbine Overspeed (P0049): a powertrain (engine/transmission) fault affecting the turbocharger / supercharger boost control. Short, gentle driving to a shop is usually possible. Most often caused by faulty boost pressure sensor, clogged intake or exhaust (DPF/cat), boost leak in intercooler piping or hoses.
• P004A — OBD2 code P004A flags a problem with the turbocharger / supercharger boost control (turbocharger/supercharger boost control "B" circuit/open). Short, gentle driving to a shop is usually possible. Common culprits: clogged intake or exhaust (DPF/cat), vacuum or actuator line damage, worn turbocharger.
• P004B — P004B — Turbocharger/Supercharger Boost Control "B" Circuit Range/Performance. A fault in the turbocharger / supercharger boost control. Short, gentle driving to a shop is usually possible. Typical causes: worn turbocharger, faulty boost pressure sensor, stuck wastegate or faulty boost control solenoid.
• P004C — Turbocharger/Supercharger Boost Control "B" Circuit Low (P004C): a powertrain (engine/transmission) fault affecting the turbocharger / supercharger boost control. Short, gentle driving to a shop is usually possible. Most often caused by worn turbocharger, boost leak in intercooler piping or hoses, clogged intake or exhaust (DPF/cat).
• P004D — OBD2 code P004D flags a problem with the turbocharger / supercharger boost control (turbocharger/supercharger boost control "B" circuit high). Short, gentle driving to a shop is usually possible. Common culprits: vacuum or actuator line damage, clogged intake or exhaust (DPF/cat), stuck wastegate or faulty boost control solenoid.
• P004E — Turbocharger/Supercharger Boost Control "A" Circuit Intermittent/Erratic (P004E): 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), stuck wastegate or faulty boost control solenoid, boost leak in intercooler piping or hoses.
• P004F — Turbocharger/Supercharger Boost Control "B" Circuit Intermittent/Erratic (P004F): 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), vacuum or actuator line damage, worn turbocharger.
• P0050 — OBD2 code P0050 flags a problem with the oxygen sensor circuit (HO2S heater control circuit (bank 2 sensor 1)). The car is usually drivable while you plan the repair. Common culprits: aged or contaminated oxygen sensor, exhaust leak near the sensor, ECM signal circuit fault.