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

• P0661 — OBD2 code P0661 flags a problem with the sensor and actuator circuits (intake manifold tuning valve control circuit low bank 1). The car is usually drivable while you plan the repair. Common culprits: control module driver fault, open or shorted wiring in the circuit, faulty sensor or actuator of the affected circuit.
• P0662 — OBD2 code P0662 flags a problem with the sensor and actuator circuits (intake manifold tuning valve control circuit high bank 1). 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.
• P0663 — Intake Manifold Tuning Valve Control Circuit/Open Bank 2 (P0663): 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, faulty sensor or actuator of the affected circuit, control module driver fault.
• P0664 — OBD2 code P0664 flags a problem with the sensor and actuator circuits (intake manifold tuning valve control circuit low bank 2). The car is usually drivable while you plan the repair. Common culprits: blown fuse feeding the circuit, open or shorted wiring in the circuit, control module driver fault.
• P0665 — P0665 — Intake Manifold Tuning Valve Control Circuit High Bank 2. A fault in the sensor and actuator circuits. The car is usually drivable while you plan the repair. Typical causes: corroded, loose or damaged connector, control module driver fault, poor ground connection.
• P0666 — P0666 — PCM/ECM/TCM Internal Temperature Sensor 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, poor ground connection, corroded, loose or damaged connector.
• P0667 — P0667 — PCM/ECM/TCM Internal Temperature Sensor 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, faulty sensor or actuator of the affected circuit, poor ground connection.
• P0668 — OBD2 code P0668 flags a problem with the sensor and actuator circuits (PCM/ECM/TCM internal temperature sensor circuit low). The car is usually drivable while you plan the repair. Common culprits: corroded, loose or damaged connector, control module driver fault, open or shorted wiring in the circuit.
• P0669 — OBD2 code P0669 flags a problem with the sensor and actuator circuits (PCM/ECM/TCM internal temperature sensor circuit high). The car is usually drivable while you plan the repair. Common culprits: blown fuse feeding the circuit, open or shorted wiring in the circuit, poor ground connection.
• P066A — P066A — Cylinder 1 Glow Plug Control Circuit Low. A fault in the diesel glow plug system. The car is usually drivable while you plan the repair. Typical causes: corroded glow plug connectors, faulty glow plug relay or control module, blown fuse in the glow plug circuit.
• P066B — Cylinder 1 Glow Plug Control Circuit High (P066B): a powertrain (engine/transmission) fault affecting the diesel glow plug system. The car is usually drivable while you plan the repair. Most often caused by damaged glow plug wiring or connector, faulty glow plug relay or control module, corroded glow plug connectors.
• P066C — Cylinder 2 Glow Plug Control Circuit Low (P066C): a powertrain (engine/transmission) fault affecting the diesel glow plug system. The car is usually drivable while you plan the repair. Most often caused by burned-out glow plug, damaged glow plug wiring or connector, blown fuse in the glow plug circuit.
• P066D — Cylinder 2 Glow Plug Control Circuit High (P066D): a powertrain (engine/transmission) fault affecting the diesel glow plug system. The car is usually drivable while you plan the repair. Most often caused by burned-out glow plug, blown fuse in the glow plug circuit, faulty glow plug relay or control module.
• P066E — P066E — Cylinder 3 Glow Plug Control Circuit Low. A fault in the diesel glow plug system. The car is usually drivable while you plan the repair. Typical causes: faulty glow plug relay or control module, damaged glow plug wiring or connector, burned-out glow plug.
• P066F — P066F — Cylinder 3 Glow Plug Control Circuit High. A fault in the diesel glow plug system. The car is usually drivable while you plan the repair. Typical causes: damaged glow plug wiring or connector, faulty glow plug relay or control module, blown fuse in the glow plug circuit.
• P0670 — P0670 — Glow Plug Module Control Circuit. 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, faulty glow plug relay or control module.
• P0671 — Cylinder 1 Glow Plug Circuit (P0671): a powertrain (engine/transmission) fault affecting the diesel glow plug system. The car is usually drivable while you plan the repair. Most often caused by corroded glow plug connectors, blown fuse in the glow plug circuit, faulty glow plug relay or control module.
• P0672 — OBD2 code P0672 flags a problem with the diesel glow plug system (cylinder 2 glow plug circuit). The car is usually drivable while you plan the repair. Common culprits: faulty glow plug relay or control module, blown fuse in the glow plug circuit, corroded glow plug connectors.
• P0673 — OBD2 code P0673 flags a problem with the diesel glow plug system (cylinder 3 glow plug circuit). The car is usually drivable while you plan the repair. Common culprits: corroded glow plug connectors, burned-out glow plug, blown fuse in the glow plug circuit.
• P0674 — Cylinder 4 Glow Plug Circuit (P0674): a powertrain (engine/transmission) fault affecting the diesel glow plug system. The car is usually drivable while you plan the repair. Most often caused by burned-out glow plug, blown fuse in the glow plug circuit, faulty glow plug relay or control module.
• P0675 — Cylinder 5 Glow Plug Circuit (P0675): a powertrain (engine/transmission) fault affecting the diesel glow plug system. The car is usually drivable while you plan the repair. Most often caused by corroded glow plug connectors, damaged glow plug wiring or connector, faulty glow plug relay or control module.
• P0676 — Cylinder 6 Glow Plug Circuit (P0676): a powertrain (engine/transmission) fault affecting the diesel glow plug system. The car is usually drivable while you plan the repair. Most often caused by corroded glow plug connectors, damaged glow plug wiring or connector, faulty glow plug relay or control module.
• P0677 — OBD2 code P0677 flags a problem with the diesel glow plug system (cylinder 7 glow plug circuit). The car is usually drivable while you plan the repair. Common culprits: blown fuse in the glow plug circuit, burned-out glow plug, corroded glow plug connectors.
• P0678 — OBD2 code P0678 flags a problem with the diesel glow plug system (cylinder 8 glow plug circuit). The car is usually drivable while you plan the repair. Common culprits: damaged glow plug wiring or connector, corroded glow plug connectors, blown fuse in the glow plug circuit.