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

• P0384 — P0384 — Glow Plug Control Module Control Circuit High. A fault in the diesel glow plug system. The car is usually drivable while you plan the repair. Typical causes: burned-out glow plug, damaged glow plug wiring or connector, blown fuse in the glow plug circuit.
• P0385 — OBD2 code P0385 flags a problem with the crankshaft position sensing (crankshaft position sensor b circuit malfunction). Driving is not recommended until fixed. Common culprits: incorrect sensor air gap, failed crankshaft position sensor, damaged sensor wiring or connector.
• P0386 — OBD2 code P0386 flags a problem with the crankshaft position sensing (crankshaft position sensor b circuit range/performance). Driving is not recommended until fixed. Common culprits: failed crankshaft position sensor, ECM signal processing fault, damaged reluctor wheel on the crankshaft.
• P0387 — P0387 flags a low-voltage condition in the crankshaft position sensor B circuit, meaning the signal stays near ground instead of toggling properly. When the PCM detects this out-of-range reading across multiple drive cycles, it stores the code and lights the check engine lamp. A failed crank sensor can cause sudden stalling with no warning, so do not continue driving with P0387 active.
• P0388 — Crankshaft Position Sensor B Circuit High Input (P0388): a powertrain (engine/transmission) fault affecting the crankshaft position sensing. Driving is not recommended until fixed. Most often caused by ECM signal processing fault, incorrect sensor air gap, damaged reluctor wheel on the crankshaft.
• P0389 — P0389 — Crankshaft Position Sensor B Circuit Intermittent. A fault in the crankshaft position sensing. Driving is not recommended until fixed. Typical causes: incorrect sensor air gap, damaged reluctor wheel on the crankshaft, failed crankshaft position sensor.
• P0390 — P0390 — Camshaft Position Sensor "B" Circuit (Bank 2). A fault in the camshaft position and variable valve timing. Short, gentle driving to a shop is usually possible. Typical causes: low or dirty engine oil affecting VVT, damaged sensor wiring or reluctor ring, faulty camshaft position sensor.
• P0391 — P0391 — Camshaft Position Sensor "B" Circuit Range/Performance (Bank 2). A fault in the camshaft position and variable valve timing. Short, gentle driving to a shop is usually possible. Typical causes: low or dirty engine oil affecting VVT, worn timing chain/belt or jumped timing, stuck or clogged VVT oil control valve (OCV).
• P0392 — OBD2 code P0392 flags a problem with the camshaft position and variable valve timing (camshaft position sensor "B" circuit low (bank 2)). Short, gentle driving to a shop is usually possible. Common culprits: worn cam phaser, faulty camshaft position sensor, low or dirty engine oil affecting VVT.
• P0393 — OBD2 code P0393 flags a problem with the camshaft position and variable valve timing (camshaft position sensor "B" circuit high (bank 2)). Short, gentle driving to a shop is usually possible. Common culprits: damaged sensor wiring or reluctor ring, worn cam phaser, worn timing chain/belt or jumped timing.
• P0394 — P0394 — Camshaft Position Sensor "B" Circuit Intermittent (Bank 2). A fault in the camshaft position and variable valve timing. Short, gentle driving to a shop is usually possible. Typical causes: damaged sensor wiring or reluctor ring, faulty camshaft position sensor, worn cam phaser.
• P0400 — P0400 — Exhaust Gas Recirculation Flow Malfunction. A fault in the exhaust gas recirculation (EGR) system. The car is usually drivable while you plan the repair. Typical causes: carbon buildup blocking the EGR valve or passages, faulty EGR solenoid or wiring, ECM control circuit fault.
• P0401 — OBD2 code P0401 flags a problem with the exhaust gas recirculation (EGR) system (exhaust gas recirculation flow insufficient detected). The car is usually drivable while you plan the repair. Common culprits: carbon buildup blocking the EGR valve or passages, ECM control circuit fault, faulty EGR solenoid or wiring.
• P0402 — P0402 — Exhaust Gas Recirculation Flow Excessive Detected. A fault in the exhaust gas recirculation (EGR) system. The car is usually drivable while you plan the repair. Typical causes: ECM control circuit fault, carbon buildup blocking the EGR valve or passages, vacuum leaks in EGR control lines.
• P0403 — P0403 — Exhaust Gas Recirculation Circuit Malfunction. A fault in the exhaust gas recirculation (EGR) system. The car is usually drivable while you plan the repair. Typical causes: ECM control circuit fault, carbon buildup blocking the EGR valve or passages, failed EGR valve or position sensor.
• P0404 — Exhaust Gas Recirculation Circuit Range/Performance (P0404): a powertrain (engine/transmission) fault affecting the exhaust gas recirculation (EGR) system. The car is usually drivable while you plan the repair. Most often caused by vacuum leaks in EGR control lines, faulty EGR solenoid or wiring, ECM control circuit fault.
• P0405 — P0405 — Exhaust Gas Recirculation Sensor A Circuit Low. A fault in the exhaust gas recirculation (EGR) system. The car is usually drivable while you plan the repair. Typical causes: ECM control circuit fault, carbon buildup blocking the EGR valve or passages, faulty EGR solenoid or wiring.
• P0406 — OBD2 code P0406 flags a problem with the exhaust gas recirculation (EGR) system (exhaust gas recirculation sensor a circuit high). The car is usually drivable while you plan the repair. Common culprits: ECM control circuit fault, faulty EGR solenoid or wiring, failed EGR valve or position sensor.
• P0407 — Exhaust Gas Recirculation Sensor B Circuit Low (P0407): a powertrain (engine/transmission) fault affecting the exhaust gas recirculation (EGR) system. The car is usually drivable while you plan the repair. Most often caused by ECM control circuit fault, carbon buildup blocking the EGR valve or passages, faulty EGR solenoid or wiring.
• P0408 — P0408 — Exhaust Gas Recirculation Sensor B Circuit High. A fault in the exhaust gas recirculation (EGR) system. The car is usually drivable while you plan the repair. Typical causes: faulty EGR solenoid or wiring, carbon buildup blocking the EGR valve or passages, ECM control circuit fault.
• P0409 — OBD2 code P0409 flags a problem with the exhaust gas recirculation (EGR) system (exhaust gas recirculation sensor "A" circuit). The car is usually drivable while you plan the repair. Common culprits: carbon buildup blocking the EGR valve or passages, faulty EGR solenoid or wiring, failed EGR valve or position sensor.
• P040A — OBD2 code P040A flags a problem with the exhaust gas recirculation (EGR) system (exhaust gas recirculation temperature sensor "A" circuit). The car is usually drivable while you plan the repair. Common culprits: faulty EGR solenoid or wiring, failed EGR valve or position sensor, ECM control circuit fault.
• P040B — Exhaust Gas Recirculation Temperature Sensor "A" Circuit Range/Performance (P040B): a powertrain (engine/transmission) fault affecting the exhaust gas recirculation (EGR) system. The car is usually drivable while you plan the repair. Most often caused by failed EGR valve or position sensor, faulty EGR solenoid or wiring, vacuum leaks in EGR control lines.
• P040C — Exhaust Gas Recirculation Temperature Sensor "A" Circuit Low (P040C): a powertrain (engine/transmission) fault affecting the exhaust gas recirculation (EGR) system. The car is usually drivable while you plan the repair. Most often caused by vacuum leaks in EGR control lines, faulty EGR solenoid or wiring, failed EGR valve or position sensor.