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.

P20DA — Exhaust Aftertreatment Fuel Supply Control Circuit High (P20DA): 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, faulty sensor or actuator of the affected circuit, corroded, loose or damaged connector.
P20DB — Exhaust Aftertreatment Fuel Supply Control Stuck Open (P20DB): 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, control module driver fault.
P20DC — Exhaust Aftertreatment Fuel Supply Control Stuck Closed (P20DC): 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, blown fuse feeding the circuit.
P20DD — P20DD — Exhaust Aftertreatment Fuel Pressure Sensor Circuit. A fault in the fuel delivery and mixture control. Short, gentle driving to a shop is usually possible. Typical causes: contaminated or incorrect fuel, faulty fuel rail pressure sensor or wiring, clogged or leaking fuel injectors.
P20DE — Exhaust Aftertreatment Fuel Pressure Sensor Circuit Range/Performance (P20DE): 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 contaminated or incorrect fuel, clogged or leaking fuel injectors, vacuum or intake leaks skewing the mixture.
P20DF — P20DF — Exhaust Aftertreatment Fuel Pressure Sensor 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, vacuum or intake leaks skewing the mixture, faulty fuel pressure regulator.
P20E0 — OBD2 code P20E0 flags a problem with the fuel delivery and mixture control (exhaust aftertreatment fuel pressure sensor circuit high). Short, gentle driving to a shop is usually possible. Common culprits: contaminated or incorrect fuel, faulty fuel pressure regulator, weak fuel pump or clogged fuel filter.
P20E1 — Exhaust Aftertreatment Fuel Pressure Sensor Circuit Intermittent/Erratic (P20E1): 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 rail pressure sensor or wiring, vacuum or intake leaks skewing the mixture, weak fuel pump or clogged fuel filter.
P20E2 — P20E2 — Exhaust Gas Temperature Sensor 1/2 Correlation Bank 1. 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.
P20E3 — P20E3 — Exhaust Gas Temperature Sensor 1/3 Correlation Bank 1. 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, blown fuse feeding the circuit, poor ground connection.
P20E4 — P20E4 — Exhaust Gas Temperature Sensor 2/3 Correlation Bank 1. 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, corroded, loose or damaged connector.
P20E5 — P20E5 — Exhaust Gas Temperature Sensor 1/2 Correlation Bank 2. 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, corroded, loose or damaged connector, poor ground connection.
P20E6 — P20E6 — Reductant Injection Air Pressure Too Low. 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.
P20E7 — OBD2 code P20E7 flags a problem with the sensor and actuator circuits (reductant injection air pressure too high). The car is usually drivable while you plan the repair. Common culprits: blown fuse feeding the circuit, corroded, loose or damaged connector, faulty sensor or actuator of the affected circuit.
P20E9 — OBD2 code P20E9 flags a problem with the sensor and actuator circuits (reductant pressure too high). The car is usually drivable while you plan the repair. Common culprits: open or shorted wiring in the circuit, blown fuse feeding the circuit, corroded, loose or damaged connector.
P20EA — P20EA — Reductant Control Module Power Relay De-Energized Performance - Too Early. 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, poor ground connection, open or shorted wiring in the circuit.
P20F0 — P20F0 — SCR NOx Catalyst - Over Temperature Bank 2. A fault in the catalytic converter efficiency monitoring. The car is usually drivable while you plan the repair. Typical causes: persistent rich or lean fuel mixture, aged or contaminated catalytic converter, exhaust leak ahead of the converter.
P20F1 — SCR NOx Pre-Catalyst - Over Temperature Bank 2 (P20F1): a powertrain (engine/transmission) fault affecting the catalytic converter efficiency monitoring. The car is usually drivable while you plan the repair. Most often caused by aged or contaminated catalytic converter, oil or coolant entering the exhaust, faulty downstream or upstream oxygen sensor.
P20F2 — P20F2 — SCR NOx Catalyst Efficiency Below Threshold Bank 2. A fault in the catalytic converter efficiency monitoring. The car is usually drivable while you plan the repair. Typical causes: exhaust leak ahead of the converter, oil or coolant entering the exhaust, engine misfires damaging the catalyst.
P20F3 — P20F3 — SCR NOx Pre- Catalyst Efficiency Below Threshold Bank 2. A fault in the catalytic converter efficiency monitoring. The car is usually drivable while you plan the repair. Typical causes: engine misfires damaging the catalyst, oil or coolant entering the exhaust, faulty downstream or upstream oxygen sensor.
P20F4 — OBD2 code P20F4 flags a problem with the sensor and actuator circuits (reductant consumption too low). The car is usually drivable while you plan the repair. Common culprits: poor ground connection, control module driver fault, open or shorted wiring in the circuit.
P20F5 — Reductant Consumption Too High (P20F5): 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, control module driver fault, blown fuse feeding the circuit.
P20F6 — OBD2 code P20F6 flags a problem with the sensor and actuator circuits (reductant injection valve stuck open bank 1 unit 1). The car is usually drivable while you plan the repair. Common culprits: open or shorted wiring in the circuit, corroded, loose or damaged connector, poor ground connection.
P20F7 — Reductant Injection Valve Stuck Open Bank 2 Unit 1 (P20F7): 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.