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

• P0991 — OBD2 code P0991 flags a problem with the automatic transmission control (transmission fluid pressure sensor/switch "E" circuit intermittent). Short, gentle driving to a shop is usually possible. Common culprits: wiring or connector faults in the valve body harness, low or degraded transmission fluid, failed shift or pressure control solenoid.
• P0992 — Transmission Fluid Pressure Sensor/Switch "F" Circuit (P0992): a powertrain (engine/transmission) fault affecting the automatic transmission control. Short, gentle driving to a shop is usually possible. Most often caused by valve body wear, faulty transmission speed sensor, low or degraded transmission fluid.
• P0993 — Transmission Fluid Pressure Sensor/Switch "F" Circuit Range/Performance (P0993): 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, internal mechanical wear (clutches, torque converter), faulty transmission speed sensor.
• P0994 — Transmission Fluid Pressure Sensor/Switch "F" Circuit Low (P0994): a powertrain (engine/transmission) fault affecting the automatic transmission control. Short, gentle driving to a shop is usually possible. Most often caused by valve body wear, failed shift or pressure control solenoid, internal mechanical wear (clutches, torque converter).
• P0995 — Transmission Fluid Pressure Sensor/Switch "F" Circuit High (P0995): 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), faulty transmission speed sensor.
• P0996 — OBD2 code P0996 flags a problem with the automatic transmission control (transmission fluid pressure sensor/switch "F" circuit intermittent). Short, gentle driving to a shop is usually possible. Common culprits: internal mechanical wear (clutches, torque converter), valve body wear, wiring or connector faults in the valve body harness.
• P0997 — Shift Solenoid "F" Control Circuit Range/Performance (P0997): 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, faulty transmission speed sensor, failed shift or pressure control solenoid.
• P0998 — Shift Solenoid "F" Control Circuit Low (P0998): a powertrain (engine/transmission) fault affecting the automatic transmission control. Short, gentle driving to a shop is usually possible. Most often caused by faulty transmission speed sensor, low or degraded transmission fluid, internal mechanical wear (clutches, torque converter).
• P0999 — OBD2 code P0999 flags a problem with the automatic transmission control (shift solenoid "F" control circuit high). 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.
• P099A — Shift Solenoid "G" Control Circuit Range/Performance (P099A): a powertrain (engine/transmission) fault affecting the automatic transmission control. Short, gentle driving to a shop is usually possible. Most often caused by faulty transmission speed sensor, low or degraded transmission fluid, wiring or connector faults in the valve body harness.
• P099B — Shift Solenoid "G" Control Circuit Low (P099B): a powertrain (engine/transmission) fault affecting the automatic transmission control. Short, gentle driving to a shop is usually possible. Most often caused by valve body wear, internal mechanical wear (clutches, torque converter), failed shift or pressure control solenoid.
• P099C — OBD2 code P099C flags a problem with the automatic transmission control (shift solenoid "G" control circuit high). Short, gentle driving to a shop is usually possible. Common culprits: low or degraded transmission fluid, internal mechanical wear (clutches, torque converter), failed shift or pressure control solenoid.
• P099D — OBD2 code P099D flags a problem with the automatic transmission control (shift solenoid "H" control circuit range/performance). Short, gentle driving to a shop is usually possible. Common culprits: faulty transmission speed sensor, wiring or connector faults in the valve body harness, internal mechanical wear (clutches, torque converter).
• P099E — OBD2 code P099E flags a problem with the automatic transmission control (shift solenoid "H" control circuit low). Short, gentle driving to a shop is usually possible. Common culprits: wiring or connector faults in the valve body harness, failed shift or pressure control solenoid, low or degraded transmission fluid.
• P099F — OBD2 code P099F flags a problem with the automatic transmission control (shift solenoid "H" control circuit high). Short, gentle driving to a shop is usually possible. Common culprits: faulty transmission speed sensor, internal mechanical wear (clutches, torque converter), valve body wear.
• P0A00 — P0A00 — Motor Electronics Coolant Temperature Sensor Circuit. A fault in the engine cooling and temperature control. Short, gentle driving to a shop is usually possible. Typical causes: thermostat stuck open or closed, water pump or radiator issues, failed cooling fan or fan relay.
• P0A01 — P0A01 — Range/Performance. 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, corroded, loose or damaged connector.
• P0A02 — P0A02 — Motor Electronics Coolant Temperature Sensor Circuit Low. A fault in the engine cooling and temperature control. Short, gentle driving to a shop is usually possible. Typical causes: failed cooling fan or fan relay, faulty coolant temperature sensor, wiring faults in the sensor circuit.
• P0A03 — OBD2 code P0A03 flags a problem with the engine cooling and temperature control (motor electronics coolant temperature sensor circuit high). Short, gentle driving to a shop is usually possible. Common culprits: faulty coolant temperature sensor, thermostat stuck open or closed, water pump or radiator issues.
• P0A04 — OBD2 code P0A04 flags a problem with the engine cooling and temperature control (motor electronics coolant temperature sensor circuit intermittent). Short, gentle driving to a shop is usually possible. Common culprits: low coolant level or air in the system, thermostat stuck open or closed, faulty coolant temperature sensor.
• P0A05 — OBD2 code P0A05 flags a problem with the engine cooling and temperature control (motor electronics coolant pump "A" control circuit/open). Short, gentle driving to a shop is usually possible. Common culprits: low coolant level or air in the system, wiring faults in the sensor circuit, failed cooling fan or fan relay.
• P0A06 — OBD2 code P0A06 flags a problem with the engine cooling and temperature control (motor electronics coolant pump "A" control circuit low). Short, gentle driving to a shop is usually possible. Common culprits: faulty coolant temperature sensor, thermostat stuck open or closed, low coolant level or air in the system.
• P0A07 — OBD2 code P0A07 flags a problem with the engine cooling and temperature control (motor electronics coolant pump "A" control circuit high). Short, gentle driving to a shop is usually possible. Common culprits: low coolant level or air in the system, faulty coolant temperature sensor, failed cooling fan or fan relay.
• P0A08 — DC/DC Converter Status Circuit (P0A08): 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, faulty sensor or actuator of the affected circuit, control module driver fault.