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

• P20C1 — Reductant Heater "C" Control Circuit/Open (P20C1): 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, poor ground connection.
• P20C2 — Reductant Heater "C" Control Circuit Performance (P20C2): 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, open or shorted wiring in the circuit, poor ground connection.
• P20C3 — P20C3 — Reductant Heater "C" Control Circuit Low. 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, blown fuse feeding the circuit.
• P20C4 — P20C4 — Reductant Heater "C" Control Circuit High. 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, open or shorted wiring in the circuit, corroded, loose or damaged connector.
• P20C5 — Reductant Heater "D" Control Circuit/Open (P20C5): 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, blown fuse feeding the circuit, faulty sensor or actuator of the affected circuit.
• P20C6 — Reductant Heater "D" Control Circuit Performance (P20C6): 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, control module driver fault.
• P20C7 — OBD2 code P20C7 flags a problem with the sensor and actuator circuits (reductant heater "D" control circuit low). The car is usually drivable while you plan the repair. Common culprits: corroded, loose or damaged connector, poor ground connection, control module driver fault.
• P20C8 — P20C8 — Reductant Heater "D" Control Circuit High. 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, corroded, loose or damaged connector, poor ground connection.
• P20C9 — Reductant Control Module Requested MIL Illumination (P20C9): 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, control module driver fault, open or shorted wiring in the circuit.
• P20CB — Exhaust Aftertreatment Fuel Injector "A" Control Circuit/Open (P20CB): 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, faulty fuel pressure regulator.
• P20CC — OBD2 code P20CC flags a problem with the fuel delivery and mixture control (exhaust aftertreatment fuel injector "A" control performance). Short, gentle driving to a shop is usually possible. Common culprits: faulty fuel pressure regulator, vacuum or intake leaks skewing the mixture, weak fuel pump or clogged fuel filter.
• P20CD — P20CD — Exhaust Aftertreatment Fuel Injector "A" Control Circuit Low. A fault in the fuel delivery and mixture control. Short, gentle driving to a shop is usually possible. Typical causes: clogged or leaking fuel injectors, vacuum or intake leaks skewing the mixture, contaminated or incorrect fuel.
• P20CE — P20CE — Exhaust Aftertreatment Fuel Injector "A" Control Circuit High. 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, contaminated or incorrect fuel, faulty fuel rail pressure sensor or wiring.
• P20CF — Exhaust Aftertreatment Fuel Injector "A" Stuck Open (P20CF): 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, contaminated or incorrect fuel.
• P20D0 — P20D0 — Exhaust Aftertreatment Fuel Injector "A" Stuck Closed. 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, faulty fuel pressure regulator.
• P20D1 — OBD2 code P20D1 flags a problem with the fuel delivery and mixture control (exhaust aftertreatment fuel injector "B" control circuit/open). Short, gentle driving to a shop is usually possible. Common culprits: contaminated or incorrect fuel, weak fuel pump or clogged fuel filter, faulty fuel rail pressure sensor or wiring.
• P20D2 — P20D2 — Exhaust Aftertreatment Fuel Injector "B" Control Performance. A fault in the fuel delivery and mixture control. Short, gentle driving to a shop is usually possible. Typical causes: contaminated or incorrect fuel, weak fuel pump or clogged fuel filter, faulty fuel pressure regulator.
• P20D3 — OBD2 code P20D3 flags a problem with the fuel delivery and mixture control (exhaust aftertreatment fuel injector "B" control circuit low). Short, gentle driving to a shop is usually possible. Common culprits: faulty fuel rail pressure sensor or wiring, weak fuel pump or clogged fuel filter, contaminated or incorrect fuel.
• P20D4 — OBD2 code P20D4 flags a problem with the fuel delivery and mixture control (exhaust aftertreatment fuel injector "B" control circuit high). Short, gentle driving to a shop is usually possible. Common culprits: clogged or leaking fuel injectors, contaminated or incorrect fuel, vacuum or intake leaks skewing the mixture.
• P20D5 — OBD2 code P20D5 flags a problem with the fuel delivery and mixture control (exhaust aftertreatment fuel injector "B" stuck open). Short, gentle driving to a shop is usually possible. Common culprits: weak fuel pump or clogged fuel filter, clogged or leaking fuel injectors, contaminated or incorrect fuel.
• P20D6 — P20D6 — Exhaust Aftertreatment Fuel Injector "B" Stuck Closed. A fault in the fuel delivery and mixture control. Short, gentle driving to a shop is usually possible. Typical causes: vacuum or intake leaks skewing the mixture, contaminated or incorrect fuel, weak fuel pump or clogged fuel filter.
• P20D7 — OBD2 code P20D7 flags a problem with the sensor and actuator circuits (exhaust aftertreatment fuel supply control circuit/open). The car is usually drivable while you plan the repair. Common culprits: poor ground connection, blown fuse feeding the circuit, control module driver fault.
• P20D8 — P20D8 — Exhaust Aftertreatment Fuel Supply Control Performance. A fault in the sensor and actuator circuits. The car is usually drivable while you plan the repair. Typical causes: control module driver fault, corroded, loose or damaged connector, poor ground connection.
• P20D9 — OBD2 code P20D9 flags a problem with the sensor and actuator circuits (exhaust aftertreatment fuel supply control circuit low). The car is usually drivable while you plan the repair. Common culprits: open or shorted wiring in the circuit, control module driver fault, faulty sensor or actuator of the affected circuit.