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.

P0278 — Cylinder 6 Contribution/Balance Fault (P0278): 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, poor ground connection.
P0279 — OBD2 code P0279 flags a problem with the fuel delivery and mixture control (cylinder 7 injector circuit low). Short, gentle driving to a shop is usually possible. Common culprits: vacuum or intake leaks skewing the mixture, contaminated or incorrect fuel, weak fuel pump or clogged fuel filter.
P0280 — OBD2 code P0280 flags a problem with the fuel delivery and mixture control (cylinder 7 injector circuit high). Short, gentle driving to a shop is usually possible. Common culprits: vacuum or intake leaks skewing the mixture, weak fuel pump or clogged fuel filter, contaminated or incorrect fuel.
P0281 — OBD2 code P0281 flags a problem with the sensor and actuator circuits (cylinder 7 contribution/balance fault). The car is usually drivable while you plan the repair. Common culprits: blown fuse feeding the circuit, poor ground connection, control module driver fault.
P0282 — P0282 — Cylinder 8 Injector Circuit Low. A fault in the fuel delivery and mixture control. Short, gentle driving to a shop is usually possible. Typical causes: faulty fuel pressure regulator, weak fuel pump or clogged fuel filter, vacuum or intake leaks skewing the mixture.
P0283 — P0283 — Cylinder 8 Injector Circuit High. A fault in the fuel delivery and mixture control. Short, gentle driving to a shop is usually possible. Typical causes: faulty fuel rail pressure sensor or wiring, weak fuel pump or clogged fuel filter, faulty fuel pressure regulator.
P0284 — Cylinder 8 Contribution/Balance Fault (P0284): 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 control module driver fault, poor ground connection, blown fuse feeding the circuit.
P0285 — Cylinder 9 Injector Circuit Low (P0285): a powertrain (engine/transmission) fault affecting the fuel delivery and mixture control. Short, gentle driving to a shop is usually possible. Most often caused by clogged or leaking fuel injectors, faulty fuel pressure regulator, weak fuel pump or clogged fuel filter.
P0286 — P0286 — Cylinder 9 Injector Circuit High. A fault in the fuel delivery and mixture control. Short, gentle driving to a shop is usually possible. Typical causes: contaminated or incorrect fuel, clogged or leaking fuel injectors, vacuum or intake leaks skewing the mixture.
P0287 — P0287 — Cylinder 9 Contribution/Balance Fault. A fault in the sensor and actuator circuits. The car is usually drivable while you plan the repair. Typical causes: control module driver fault, blown fuse feeding the circuit, corroded, loose or damaged connector.
P0288 — Cylinder 10 Injector Circuit Low (P0288): a powertrain (engine/transmission) fault affecting the fuel delivery and mixture control. Short, gentle driving to a shop is usually possible. Most often caused by weak fuel pump or clogged fuel filter, clogged or leaking fuel injectors, vacuum or intake leaks skewing the mixture.
P0289 — Cylinder 10 Injector Circuit High (P0289): a powertrain (engine/transmission) fault affecting the fuel delivery and mixture control. Short, gentle driving to a shop is usually possible. Most often caused by faulty fuel pressure regulator, faulty fuel rail pressure sensor or wiring, weak fuel pump or clogged fuel filter.
P0290 — OBD2 code P0290 flags a problem with the sensor and actuator circuits (cylinder 10 contribution/balance fault). 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.
P0291 — P0291 — Cylinder 11 Injector Circuit Low. A fault in the fuel delivery and mixture control. Short, gentle driving to a shop is usually possible. Typical causes: weak fuel pump or clogged fuel filter, faulty fuel pressure regulator, vacuum or intake leaks skewing the mixture.
P0292 — OBD2 code P0292 flags a problem with the fuel delivery and mixture control (cylinder 11 injector circuit high). Short, gentle driving to a shop is usually possible. Common culprits: faulty fuel pressure regulator, clogged or leaking fuel injectors, contaminated or incorrect fuel.
P0293 — P0293 signals a cylinder 11 contribution/balance fault, meaning the engine computer has detected a sensor or actuator circuit for that cylinder operating outside acceptable parameters. In most cases your vehicle stays drivable, though you might notice sluggish acceleration or slightly higher fuel usage. The fix ranges from a simple connector repair to component replacement, depending on what's actually failed. Address it before it strands you or causes secondary damage to oth
P0294 — P0294 — Cylinder 12 Injector Circuit Low. A fault in the fuel delivery and mixture control. Short, gentle driving to a shop is usually possible. Typical causes: faulty fuel rail pressure sensor or wiring, weak fuel pump or clogged fuel filter, clogged or leaking fuel injectors.
P0295 — OBD2 code P0295 flags a problem with the fuel delivery and mixture control (cylinder 12 injector circuit high). Short, gentle driving to a shop is usually possible. Common culprits: faulty fuel pressure regulator, faulty fuel rail pressure sensor or wiring, clogged or leaking fuel injectors.
P0296 — Cylinder 12 Contribution/Range Fault (P0296): 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, faulty sensor or actuator of the affected circuit.
P0297 — Vehicle Overspeed Condition (P0297): 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, faulty sensor or actuator of the affected circuit.
P0298 — Engine Oil Over Temperature Condition (P0298): 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 control module driver fault, open or shorted wiring in the circuit, blown fuse feeding the circuit.
P0299 — P0299 — Turbocharger/Supercharger "A" Underboost Condition. A fault in the turbocharger / supercharger boost control. Short, gentle driving to a shop is usually possible. Typical causes: stuck wastegate or faulty boost control solenoid, clogged intake or exhaust (DPF/cat), vacuum or actuator line damage.
P029A — P029A — Cylinder 1 - Fuel Trim at Max Limit. A fault in the fuel delivery and mixture control. Short, gentle driving to a shop is usually possible. Typical causes: faulty fuel rail pressure sensor or wiring, clogged or leaking fuel injectors, contaminated or incorrect fuel.
P029B — Cylinder 1 - Fuel Trim at Min Limit (P029B): a powertrain (engine/transmission) fault affecting the fuel delivery and mixture control. Short, gentle driving to a shop is usually possible. Most often caused by weak fuel pump or clogged fuel filter, vacuum or intake leaks skewing the mixture, faulty fuel rail pressure sensor or wiring.