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

• P071F — OBD2 code P071F flags a problem with the automatic transmission control (transmission mode switch "B" circuit high). Short, gentle driving to a shop is usually possible. Common culprits: low or degraded transmission fluid, faulty transmission speed sensor, wiring or connector faults in the valve body harness.
• P0720 — Output Speed Sensor Circuit Malfunction (P0720): 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, poor ground connection.
• P0721 — OBD2 code P0721 flags a problem with the sensor and actuator circuits (output speed sensor range/performance). The car is usually drivable while you plan the repair. Common culprits: faulty sensor or actuator of the affected circuit, control module driver fault, open or shorted wiring in the circuit.
• P0722 — Output Speed Sensor No Signal (P0722): 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, poor ground connection, control module driver fault.
• P0723 — Output Speed Sensor Intermittent (P0723): 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, control module driver fault, open or shorted wiring in the circuit.
• P0724 — OBD2 code P0724 flags a problem with the automatic transmission control (torque converter/brake switch b circuit high). Short, gentle driving to a shop is usually possible. Common culprits: internal mechanical wear (clutches, torque converter), low or degraded transmission fluid, faulty transmission speed sensor.
• P0725 — OBD2 code P0725 flags a problem with the sensor and actuator circuits (engine speed input circuit malfunction). The car is usually drivable while you plan the repair. Common culprits: blown fuse feeding the circuit, faulty sensor or actuator of the affected circuit, open or shorted wiring in the circuit.
• P0726 — OBD2 code P0726 flags a problem with the sensor and actuator circuits (engine speed input circuit range/performance). The car is usually drivable while you plan the repair. Common culprits: control module driver fault, faulty sensor or actuator of the affected circuit, poor ground connection.
• P0727 — OBD2 code P0727 flags a problem with the sensor and actuator circuits (engine speed input circuit no signal). 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.
• P0728 — Engine Speed Input Circuit Intermittent (P0728): 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.
• P0729 — OBD2 code P0729 flags a problem with the sensor and actuator circuits (gear 6 incorrect ratio). The car is usually drivable while you plan the repair. Common culprits: open or shorted wiring in the circuit, poor ground connection, corroded, loose or damaged connector.
• P072A — P072A — Stuck in Neutral. 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, faulty sensor or actuator of the affected circuit, poor ground connection.
• P072B — OBD2 code P072B flags a problem with the sensor and actuator circuits (stuck in reverse). The car is usually drivable while you plan the repair. Common culprits: poor ground connection, faulty sensor or actuator of the affected circuit, corroded, loose or damaged connector.
• P072C — OBD2 code P072C flags a problem with the sensor and actuator circuits (stuck in gear 1). 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, corroded, loose or damaged connector.
• P072D — Stuck in Gear 2 (P072D): 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, blown fuse feeding the circuit.
• P072E — Stuck in Gear 3 (P072E): 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, open or shorted wiring in the circuit, corroded, loose or damaged connector.
• P072F — P072F — Stuck in Gear 4. A fault in the sensor and actuator circuits. The car is usually drivable while you plan the repair. Typical causes: control module driver fault, corroded, loose or damaged connector, open or shorted wiring in the circuit.
• P0730 — P0730 — Incorrect Gear Ratio. A fault in the automatic transmission control. Short, gentle driving to a shop is usually possible. Typical causes: internal mechanical wear (clutches, torque converter), wiring or connector faults in the valve body harness, failed shift or pressure control solenoid.
• P0731 — OBD2 code P0731 flags a problem with the sensor and actuator circuits (gear i incorrect ratio). The car is usually drivable while you plan the repair. Common culprits: faulty sensor or actuator of the affected circuit, corroded, loose or damaged connector, control module driver fault.
• P0732 — P0732 — Gear 2 Incorrect ratio. 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, faulty sensor or actuator of the affected circuit, poor ground connection.
• P0733 — P0733 — Gear 3 Incorrect ratio. 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, control module driver fault, poor ground connection.
• P0734 — OBD2 code P0734 flags a problem with the sensor and actuator circuits (gear 4 incorrect ratio). The car is usually drivable while you plan the repair. Common culprits: poor ground connection, blown fuse feeding the circuit, corroded, loose or damaged connector.
• P0735 — P0735 — Gear 5 Incorrect ratio. 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.
• P0736 — P0736 — Reverse incorrect gear ratio. A fault in the automatic transmission control. Short, gentle driving to a shop is usually possible. Typical causes: faulty transmission speed sensor, internal mechanical wear (clutches, torque converter), failed shift or pressure control solenoid.