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

• P0649 — OBD2 code P0649 flags a problem with the sensor and actuator circuits (speed control lamp control circuit). The car is usually drivable while you plan the repair. Common culprits: faulty sensor or actuator of the affected circuit, blown fuse feeding the circuit, poor ground connection.
• P064A — OBD2 code P064A flags a problem with the fuel delivery and mixture control (fuel pump control module). Short, gentle driving to a shop is usually possible. Common culprits: faulty fuel pressure regulator, faulty fuel rail pressure sensor or wiring, contaminated or incorrect fuel.
• P064B — P064B — PTO Control Module. A fault in the sensor and actuator circuits. The car is usually drivable while you plan the repair. Typical causes: poor ground connection, control module driver fault, blown fuse feeding the circuit.
• P064C — Glow Plug Control Module (P064C): 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, burned-out glow plug.
• P064D — P064D — Internal Control Module O2 Sensor Processor Performance Bank 1. A fault in the oxygen sensor circuit. The car is usually drivable while you plan the repair. Typical causes: oil or coolant contamination of the sensor tip, exhaust leak near the sensor, aged or contaminated oxygen sensor.
• P064E — P064E — Internal Control Module O2 Sensor Processor Performance Bank 2. A fault in the oxygen sensor circuit. The car is usually drivable while you plan the repair. Typical causes: oil or coolant contamination of the sensor tip, aged or contaminated oxygen sensor, exhaust leak near the sensor.
• P064F — P064F — Unauthorized Software/Calibration Detected. A fault in the sensor and actuator circuits. The car is usually drivable while you plan the repair. Typical causes: faulty sensor or actuator of the affected circuit, corroded, loose or damaged connector, poor ground connection.
• P0650 — Malfunction Indicator Lamp (MIL) Control Circuit Malfunction (P0650): 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, open or shorted wiring in the circuit.
• P0651 — Sensor Reference Voltage "B" Circuit Open (P0651): 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.
• P0652 — OBD2 code P0652 flags a problem with the sensor and actuator circuits (sensor reference voltage "B" circuit low). The car is usually drivable while you plan the repair. Common culprits: control module driver fault, corroded, loose or damaged connector, blown fuse feeding the circuit.
• P0653 — P0653 — Sensor Reference Voltage "B" Circuit High. 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, control module driver fault, faulty sensor or actuator of the affected circuit.
• P0654 — Engine RPM Output Circuit Malfunction (P0654): 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, open or shorted wiring in the circuit.
• P0655 — P0655 — Engine Hot Lamp Output Control Circuit Malfunction. 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, corroded, loose or damaged connector, poor ground connection.
• P0656 — OBD2 code P0656 flags a problem with the fuel delivery and mixture control (fuel level output circuit malfunction). Short, gentle driving to a shop is usually possible. Common culprits: clogged or leaking fuel injectors, contaminated or incorrect fuel, weak fuel pump or clogged fuel filter.
• P0657 — OBD2 code P0657 flags a problem with the sensor and actuator circuits (actuator supply voltage "A" circuit/open). The car is usually drivable while you plan the repair. Common culprits: corroded, loose or damaged connector, poor ground connection, control module driver fault.
• P0658 — Actuator Supply Voltage "A" Circuit Low (P0658): 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, corroded, loose or damaged connector, control module driver fault.
• P0659 — OBD2 code P0659 flags a problem with the sensor and actuator circuits (actuator supply voltage "A" circuit high). The car is usually drivable while you plan the repair. Common culprits: faulty sensor or actuator of the affected circuit, poor ground connection, control module driver fault.
• P065A — P065A — Generator System Performance. 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, faulty sensor or actuator of the affected circuit, poor ground connection.
• P065B — Generator Control Circuit Range/Performance (P065B): 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, blown fuse feeding the circuit, faulty sensor or actuator of the affected circuit.
• P065C — Generator Mechanical Performance (P065C): 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 faulty sensor or actuator of the affected circuit, corroded, loose or damaged connector, open or shorted wiring in the circuit.
• P065D — P065D — Reductant System Malfunction Lamp Control 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, corroded, loose or damaged connector, poor ground connection.
• P065E — Intake Manifold Tuning Valve Performance Bank 1 (P065E): 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.
• P065F — P065F — Intake Manifold Tuning Valve Performance 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.
• P0660 — Intake Manifold Tuning Valve Control Circuit/Open Bank 1 (P0660): 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, blown fuse feeding the circuit, corroded, loose or damaged connector.