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

• P2788 — P2788 — Auto Shift Manual Adaptive Learning at Limit. 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, control module driver fault.
• P2789 — P2789 — Clutch "A" Adaptive Learning at Limit. 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.
• P278A — Kick Down Switch Circuit (P278A): 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.
• P278B — OBD2 code P278B flags a problem with the sensor and actuator circuits (kick down switch circuit range/performance). The car is usually drivable while you plan the repair. Common culprits: control module driver fault, poor ground connection, corroded, loose or damaged connector.
• P278C — P278C — Kick Down Switch Circuit Low. A fault in the sensor and actuator circuits. The car is usually drivable while you plan the repair. Typical causes: control module driver fault, poor ground connection, corroded, loose or damaged connector.
• P278D — Kick Down Switch Circuit High (P278D): 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, blown fuse feeding the circuit, corroded, loose or damaged connector.
• P278E — Kick Down Switch Circuit Intermittent/Erratic (P278E): 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.
• P278F — OBD2 code P278F flags a problem with the sensor and actuator circuits (clutch "B" adaptive learning at limit). The car is usually drivable while you plan the repair. Common culprits: blown fuse feeding the circuit, poor ground connection, faulty sensor or actuator of the affected circuit.
• P2790 — P2790 — Gate Select Direction Circuit. 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, faulty sensor or actuator of the affected circuit.
• P2791 — Gate Select Direction Circuit Low (P2791): 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, blown fuse feeding the circuit.
• P2792 — Gate Select Direction Circuit High (P2792): 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, poor ground connection, faulty sensor or actuator of the affected circuit.
• P2794 — OBD2 code P2794 flags a problem with the automatic transmission control (gear shift direction circuit low). Short, gentle driving to a shop is usually possible. Common culprits: faulty transmission speed sensor, low or degraded transmission fluid, internal mechanical wear (clutches, torque converter).
• P2795 — P2795 — Gear Shift Direction Circuit High. A fault in the automatic transmission control. Short, gentle driving to a shop is usually possible. Typical causes: failed shift or pressure control solenoid, faulty transmission speed sensor, valve body wear.
• P2797 — P2797 — Auxiliary Transmission Fluid Pump Performance. A fault in the automatic transmission control. Short, gentle driving to a shop is usually possible. Typical causes: faulty transmission speed sensor, wiring or connector faults in the valve body harness, failed shift or pressure control solenoid.
• P2798 — Auxiliary Transmission Fluid Pump Control Circuit Low (P2798): a powertrain (engine/transmission) fault affecting the automatic transmission control. Short, gentle driving to a shop is usually possible. Most often caused by failed shift or pressure control solenoid, internal mechanical wear (clutches, torque converter), low or degraded transmission fluid.
• P2799 — OBD2 code P2799 flags a problem with the automatic transmission control (auxiliary transmission fluid pump control circuit high). Short, gentle driving to a shop is usually possible. Common culprits: internal mechanical wear (clutches, torque converter), wiring or connector faults in the valve body harness, faulty transmission speed sensor.
• P279A — Transfer Case Gear High Incorrect Ratio (P279A): 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, blown fuse feeding the circuit.
• P279B — OBD2 code P279B flags a problem with the sensor and actuator circuits (transfer case gear low incorrect ratio). The car is usually drivable while you plan the repair. Common culprits: blown fuse feeding the circuit, corroded, loose or damaged connector, poor ground connection.
• P279C — OBD2 code P279C flags a problem with the sensor and actuator circuits (transfer case gear neutral incorrect ratio). The car is usually drivable while you plan the repair. Common culprits: faulty sensor or actuator of the affected circuit, poor ground connection, open or shorted wiring in the circuit.
• P279D — P279D — Four Wheel Drive (4WD) Range Signal Circuit. 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, blown fuse feeding the circuit, control module driver fault.
• P279E — P279E — Four Wheel Drive (4WD) Range Signal Circuit Range/Performance. A fault in the sensor and actuator circuits. The car is usually drivable while you plan the repair. Typical causes: poor ground connection, open or shorted wiring in the circuit, control module driver fault.
• P279F — OBD2 code P279F flags a problem with the sensor and actuator circuits (four wheel drive (4WD) range signal circuit low). The car is usually drivable while you plan the repair. Common culprits: control module driver fault, faulty sensor or actuator of the affected circuit, corroded, loose or damaged connector.
• P27A0 — Four Wheel Drive (4WD) Range Signal Circuit High (P27A0): 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, blown fuse feeding the circuit, poor ground connection.
• P2800 — OBD2 code P2800 flags a problem with the automatic transmission control (transmission range sensor "B" circuit (PRNDL input)). 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.