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.

P20A7 — P20A7 — Reductant Injection Air Pressure Control Valve 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, control module driver fault.
P20A8 — P20A8 — Reductant Injection Air Pressure Control Valve 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, faulty sensor or actuator of the affected circuit, blown fuse feeding the circuit.
P20A9 — P20A9 — Reductant Injection Air Pressure Control Valve 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, faulty sensor or actuator of the affected circuit, poor ground connection.
P20AA — OBD2 code P20AA flags a problem with the sensor and actuator circuits (reductant injection air pressure control valve stuck open). The car is usually drivable while you plan the repair. Common culprits: corroded, loose or damaged connector, open or shorted wiring in the circuit, blown fuse feeding the circuit.
P20AB — OBD2 code P20AB flags a problem with the sensor and actuator circuits (reductant injection air pressure control valve stuck closed). The car is usually drivable while you plan the repair. Common culprits: blown fuse feeding the circuit, poor ground connection, open or shorted wiring in the circuit.
P20AD — P20AD — Reductant Metering Unit Temperature Sensor Circuit Range/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, poor ground connection, open or shorted wiring in the circuit.
P20AE — Reductant Metering Unit Temperature Sensor Circuit Low (P20AE): 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 corroded, loose or damaged connector, open or shorted wiring in the circuit, control module driver fault.
P20AF — OBD2 code P20AF flags a problem with the sensor and actuator circuits (reductant metering unit temperature sensor circuit high). The car is usually drivable while you plan the repair. Common culprits: corroded, loose or damaged connector, open or shorted wiring in the circuit, faulty sensor or actuator of the affected circuit.
P20B0 — Reductant Metering Unit Temperature Sensor Circuit Intermittent/Erratic (P20B0): 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 corroded, loose or damaged connector, control module driver fault, poor ground connection.
P20B1 — P20B1 — Reductant Heater Coolant Control Valve Circuit/Open. 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, wiring faults in the sensor circuit, water pump or radiator issues.
P20B2 — Reductant Heater Coolant Control Valve Performance (P20B2): a powertrain (engine/transmission) fault affecting the engine cooling and temperature control. Short, gentle driving to a shop is usually possible. Most often caused by thermostat stuck open or closed, wiring faults in the sensor circuit, low coolant level or air in the system.
P20B3 — P20B3 — Reductant Heater Coolant Control Valve Circuit Low. 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, low coolant level or air in the system, wiring faults in the sensor circuit.
P20B4 — P20B4 — Reductant Heater Coolant Control Valve Circuit High. 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, wiring faults in the sensor circuit, faulty coolant temperature sensor.
P20B5 — OBD2 code P20B5 flags a problem with the sensor and actuator circuits (reductant metering unit heater control circuit/open). The car is usually drivable while you plan the repair. Common culprits: poor ground connection, corroded, loose or damaged connector, faulty sensor or actuator of the affected circuit.
P20B6 — Reductant Metering Unit Heater Control Circuit Performance (P20B6): 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 corroded, loose or damaged connector, open or shorted wiring in the circuit, poor ground connection.
P20B7 — Reductant Metering Unit Heater Control Circuit Low (P20B7): 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, blown fuse feeding the circuit, poor ground connection.
P20B8 — P20B8 — Reductant Metering Unit Heater Control Circuit High. A fault in the sensor and actuator circuits. The car is usually drivable while you plan the repair. Typical causes: poor ground connection, control module driver fault, corroded, loose or damaged connector.
P20B9 — Reductant Heater "A" Control Circuit/Open (P20B9): 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, corroded, loose or damaged connector.
P20BA — OBD2 code P20BA flags a problem with the sensor and actuator circuits (reductant heater "A" control circuit performance). The car is usually drivable while you plan the repair. Common culprits: control module driver fault, open or shorted wiring in the circuit, corroded, loose or damaged connector.
P20BB — Reductant Heater "A" Control Circuit Low (P20BB): 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, poor ground connection, control module driver fault.
P20BD — P20BD — Reductant Heater "B" Control Circuit/Open. 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, blown fuse feeding the circuit.
P20BE — Reductant Heater "B" Control Circuit Performance (P20BE): 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 corroded, loose or damaged connector, control module driver fault, blown fuse feeding the circuit.
P20BF — Reductant Heater "B" Control Circuit Low (P20BF): 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, corroded, loose or damaged connector.
P20C0 — Reductant Heater "B" Control Circuit High (P20C0): 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, corroded, loose or damaged connector, blown fuse feeding the circuit.