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

• P1663 — P1663 — Recirculation Override Circuit Malfunction. 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, poor ground connection, control module driver fault.
• P1664 — P1664 — Injection Pump Control Module Malfunction. P1664 can interfere with injection-pump command delivery.
• P1665 — P1665 — Injection Pump Control Module Communication Loss. Loss of communication with the injection pump control module can cause poor engine operation, unexpected stalling, or failure to restart.
• P1666 — P1666 — ECM and Pump Crank Synchronization. P1666 can cause unstable cranking, rough running, loss of power, or stalling.
• P1668 — P1668 — Output Circuit Check Signal High. A fault in the sensor and actuator circuits. The car is usually drivable while you plan the repair. Typical causes: control module driver fault, open or shorted wiring in the circuit, blown fuse feeding the circuit.
• P1669 — P1669 — Injection Pump Module Monitor Fault. P1669 can indicate that the ECM cannot properly monitor the injection pump control module.
• P1670 — P1670 — Output Circuit Check Signal Low. A fault in the sensor and actuator circuits. The car is usually drivable while you plan the repair. Typical causes: poor ground connection, corroded, loose or damaged connector, faulty sensor or actuator of the affected circuit.
• P1671 — P1671 — Secondary Fuel Pump Relay Control Fault. P1671 can leave the secondary fuel-pump function unavailable and may reduce fuel-system redundancy.
• P1673 — P1673 — ABS Lamp Control Circuit. P1673 concerns the ABS warning-lamp circuit and does not by itself prove that the ABS hydraulic system has failed.
• P1674 — P1674 — Control Module Circuit Fault. P1674 alone does not identify which vehicle function is impaired.
• P1675 — P1675 — Injector Data Signal Malfunction. P1675 does not automatically require stopping if the engine runs smoothly, but the fault should be diagnosed promptly.
• P1676 — P1676 — Injector Data Signal Fault. P1676 can affect injector control and may cause rough running, hesitation, or stalling.
• P1677 — P1677 — Alternative Fuel Module Communication Failure. P1677 can cause the powertrain controller to use a default fuel strategy, producing hesitation, misfires, or stalling.
• P1678 — P1678 — Oil Low-Pressure Lamp Control Circuit Fault. Do not rely on the warning lamp while P1678 is active.
• P1680 — P1680 — IDM_EN Circuit Failure. 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, corroded, loose or damaged connector.
• P1681 — P1681 — Fuel Demand Command Signal Circuit Malfunction. 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.
• P1682 — OBD2 code P1682 flags a problem with the sensor and actuator circuits (CI circuit malfunction). The car is usually drivable while you plan the repair. Common culprits: faulty sensor or actuator of the affected circuit, poor ground connection, corroded, loose or damaged connector.
• P1683 — OBD2 code P1683 flags a problem with the sensor and actuator circuits (PCM - IDM communications error). The car is usually drivable while you plan the repair. Common culprits: open or shorted wiring in the circuit, corroded, loose or damaged connector, control module driver fault.
• P1684 — OBD2 code P1684 flags a problem with the sensor and actuator circuits (electronic feedback signal not detected). 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.
• P1685 — P1685 — Metering Oil Pump Malfunction. 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, poor ground connection, open or shorted wiring in the circuit.
• P1686 — Metering Oil Pump Malfunction (P1686): 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, corroded, loose or damaged connector, control module driver fault.
• P1687 — P1687 — Metering Oil Pump Malfunction. 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, open or shorted wiring in the circuit, control module driver fault.
• P1688 — P1688 — Metering Oil Pump Temperature Sensor Circuit Malfunction. 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, poor ground connection, control module driver fault.
• P1689 — P1689 — Metering Oil Pump Position Sensor Circuit Malfunction. 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.