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

• P0737 — P0737 — TCM Engine Speed Output Circuit. 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, control module driver fault, corroded, loose or damaged connector.
• P0738 — TCM Engine Speed Output Circuit Low (P0738): 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, blown fuse feeding the circuit.
• P0739 — TCM Engine Speed Output Circuit High (P0739): 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, control module driver fault.
• P073A — P073A — Stuck in Gear 5. 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, control module driver fault, open or shorted wiring in the circuit.
• P073B — OBD2 code P073B flags a problem with the sensor and actuator circuits (stuck in gear 6). The car is usually drivable while you plan the repair. Common culprits: control module driver fault, faulty sensor or actuator of the affected circuit, open or shorted wiring in the circuit.
• P073C — P073C — Stuck in Gear 7. 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, open or shorted wiring in the circuit, poor ground connection.
• P073D — P073D — Unable to Engage Neutral. A fault in the sensor and actuator circuits. The car is usually drivable while you plan the repair. Typical causes: poor ground connection, faulty sensor or actuator of the affected circuit, control module driver fault.
• P073E — P073E — Unable to Engage Reverse. 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.
• P073F — P073F — Unable to Engage Gear 1. 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.
• P0740 — Torque Converter Clutch Circuit Malfunction (P0740): a powertrain (engine/transmission) fault affecting the automatic transmission control. Short, gentle driving to a shop is usually possible. Most often caused by low or degraded transmission fluid, wiring or connector faults in the valve body harness, valve body wear.
• P0741 — Torque Converter Clutch Circuit Performance or Stuck Off (P0741): a powertrain (engine/transmission) fault affecting the automatic transmission control. Short, gentle driving to a shop is usually possible. Most often caused by wiring or connector faults in the valve body harness, failed shift or pressure control solenoid, low or degraded transmission fluid.
• P0742 — Torque Converter Clutch Circuit Stock On (P0742): a powertrain (engine/transmission) fault affecting the automatic transmission control. Short, gentle driving to a shop is usually possible. Most often caused by wiring or connector faults in the valve body harness, failed shift or pressure control solenoid, faulty transmission speed sensor.
• P0743 — P0743 — Torque Converter Clutch Circuit Electrical. A fault in the automatic transmission control. Short, gentle driving to a shop is usually possible. Typical causes: faulty transmission speed sensor, valve body wear, internal mechanical wear (clutches, torque converter).
• P0744 — P0744 — Torque Converter Clutch Circuit Intermittent. A fault in the automatic transmission control. Short, gentle driving to a shop is usually possible. Typical causes: internal mechanical wear (clutches, torque converter), low or degraded transmission fluid, valve body wear.
• P0745 — P0745 — Pressure Control Solenoid A Malfunction. A fault in the automatic transmission control. Short, gentle driving to a shop is usually possible. Typical causes: internal mechanical wear (clutches, torque converter), valve body wear, failed shift or pressure control solenoid.
• P0746 — OBD2 code P0746 flags a problem with the automatic transmission control (pressure control solenoid a performance or stuck off). Short, gentle driving to a shop is usually possible. Common culprits: low or degraded transmission fluid, failed shift or pressure control solenoid, faulty transmission speed sensor.
• P0747 — OBD2 code P0747 flags a problem with the automatic transmission control (pressure control solenoid a stuck on). Short, gentle driving to a shop is usually possible. Common culprits: low or degraded transmission fluid, wiring or connector faults in the valve body harness, faulty transmission speed sensor.
• P0748 — OBD2 code P0748 flags a problem with the automatic transmission control (pressure control solenoid a electrical). Short, gentle driving to a shop is usually possible. Common culprits: valve body wear, faulty transmission speed sensor, wiring or connector faults in the valve body harness.
• P0749 — Pressure Control Solenoid A Intermittent (P0749): a powertrain (engine/transmission) fault affecting the automatic transmission control. Short, gentle driving to a shop is usually possible. Most often caused by low or degraded transmission fluid, valve body wear, internal mechanical wear (clutches, torque converter).
• P074A — Unable To Engage Gear 2 (P074A): 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.
• P074B — OBD2 code P074B flags a problem with the sensor and actuator circuits (unable to engage gear 3). The car is usually drivable while you plan the repair. Common culprits: corroded, loose or damaged connector, poor ground connection, control module driver fault.
• P074C — P074C — Unable To Engage Gear 4. 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, blown fuse feeding the circuit, poor ground connection.
• P074D — P074D — Unable To Engage Gear 5. 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, poor ground connection, blown fuse feeding the circuit.
• P074E — OBD2 code P074E flags a problem with the sensor and actuator circuits (unable to engage gear 6). The car is usually drivable while you plan the repair. Common culprits: blown fuse feeding the circuit, control module driver fault, faulty sensor or actuator of the affected circuit.