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.

P0534 — P0534 — Air Conditioner Refrigerant Charge Loss. 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, faulty sensor or actuator of the affected circuit.
P0535 — A/C Evaporator Temperature Sensor Circuit (P0535): a powertrain (engine/transmission) fault affecting the evaporative emission (EVAP) system. The car is usually drivable while you plan the repair. Most often caused by faulty purge valve (canister purge solenoid), faulty vent valve or leak detection pump, saturated or damaged charcoal canister.
P0536 — P0536 — A/C Evaporator Temperature Sensor Circuit Range/Performance. A fault in the evaporative emission (EVAP) system. The car is usually drivable while you plan the repair. Typical causes: saturated or damaged charcoal canister, cracked EVAP hoses or lines, loose, damaged or wrong fuel cap.
P0537 — P0537 — A/C Evaporator Temperature Sensor Circuit Low. A fault in the evaporative emission (EVAP) system. The car is usually drivable while you plan the repair. Typical causes: faulty vent valve or leak detection pump, small leak in the fuel tank or filler neck, cracked EVAP hoses or lines.
P0538 — A/C Evaporator Temperature Sensor Circuit High (P0538): a powertrain (engine/transmission) fault affecting the evaporative emission (EVAP) system. The car is usually drivable while you plan the repair. Most often caused by faulty purge valve (canister purge solenoid), loose, damaged or wrong fuel cap, small leak in the fuel tank or filler neck.
P0539 — OBD2 code P0539 flags a problem with the evaporative emission (EVAP) system (A/C evaporator temperature sensor circuit intermittent). The car is usually drivable while you plan the repair. Common culprits: small leak in the fuel tank or filler neck, loose, damaged or wrong fuel cap, faulty purge valve (canister purge solenoid).
P053A — OBD2 code P053A flags a problem with the sensor and actuator circuits (positive crankcase ventilation heater control circuit /open). The car is usually drivable while you plan the repair. Common culprits: poor ground connection, control module driver fault, blown fuse feeding the circuit.
P053B — Positive Crankcase Ventilation Heater Control Circuit Low (P053B): 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, faulty sensor or actuator of the affected circuit, corroded, loose or damaged connector.
P053C — OBD2 code P053C flags a problem with the sensor and actuator circuits (positive crankcase ventilation heater control circuit high). The car is usually drivable while you plan the repair. Common culprits: corroded, loose or damaged connector, blown fuse feeding the circuit, open or shorted wiring in the circuit.
P0540 — OBD2 code P0540 flags a problem with the throttle and intake air metering (intake air heater "A" circuit). Short, gentle driving to a shop is usually possible. Common culprits: intake air leaks after the MAF sensor, dirty throttle body or stuck throttle plate, failed electronic throttle motor.
P0541 — P0541 — Intake Air Heater "A" Circuit Low. A fault in the throttle and intake air metering. Short, gentle driving to a shop is usually possible. Typical causes: wiring or connector faults in the throttle circuit, contaminated or failed MAF/MAP sensor, faulty throttle position sensor or pedal sensor.
P0542 — OBD2 code P0542 flags a problem with the throttle and intake air metering (intake air heater "A" circuit high). Short, gentle driving to a shop is usually possible. Common culprits: intake air leaks after the MAF sensor, contaminated or failed MAF/MAP sensor, wiring or connector faults in the throttle circuit.
P0543 — P0543 — Intake Air Heater "A" Circuit Open. A fault in the throttle and intake air metering. Short, gentle driving to a shop is usually possible. Typical causes: intake air leaks after the MAF sensor, dirty throttle body or stuck throttle plate, failed electronic throttle motor.
P0544 — Exhaust Gas Temperature Sensor Circuit (Bank 1 Sensor 1) (P0544): 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, blown fuse feeding the circuit, corroded, loose or damaged connector.
P0545 — OBD2 code P0545 flags a problem with the sensor and actuator circuits (exhaust gas temperature sensor circuit low (bank 1 sensor 1)). The car is usually drivable while you plan the repair. Common culprits: corroded, loose or damaged connector, control module driver fault, poor ground connection.
P0546 — Exhaust Gas Temperature Sensor Circuit High (Bank 1 Sensor 1) (P0546): 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, corroded, loose or damaged connector, faulty sensor or actuator of the affected circuit.
P0547 — P0547 — Exhaust Gas Temperature Sensor Circuit (Bank 2 Sensor 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, corroded, loose or damaged connector, control module driver fault.
P0548 — P0548 — Exhaust Gas Temperature Sensor Circuit Low (Bank 2 Sensor 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, faulty sensor or actuator of the affected circuit, poor ground connection.
P0549 — OBD2 code P0549 flags a problem with the sensor and actuator circuits (exhaust gas temperature sensor circuit high (bank 2 sensor 1)). The car is usually drivable while you plan the repair. Common culprits: control module driver fault, poor ground connection, faulty sensor or actuator of the affected circuit.
P054A — P054A — Cold Start "B" Camshaft Position Timing Over-Advanced Bank 1. A fault in the camshaft position and variable valve timing. Short, gentle driving to a shop is usually possible. Typical causes: stuck or clogged VVT oil control valve (OCV), damaged sensor wiring or reluctor ring, low or dirty engine oil affecting VVT.
P054B — Cold Start "B" Camshaft Position Timing Over-Retarded Bank 1 (P054B): a powertrain (engine/transmission) fault affecting the camshaft position and variable valve timing. Short, gentle driving to a shop is usually possible. Most often caused by damaged sensor wiring or reluctor ring, low or dirty engine oil affecting VVT, worn timing chain/belt or jumped timing.
P054C — P054C — Cold Start "B" Camshaft Position Timing Over-Advanced Bank 2. A fault in the camshaft position and variable valve timing. Short, gentle driving to a shop is usually possible. Typical causes: worn cam phaser, worn timing chain/belt or jumped timing, stuck or clogged VVT oil control valve (OCV).
P054D — Cold Start "B" Camshaft Position Timing Over-Retarded Bank 2 (P054D): a powertrain (engine/transmission) fault affecting the camshaft position and variable valve timing. Short, gentle driving to a shop is usually possible. Most often caused by damaged sensor wiring or reluctor ring, worn cam phaser, worn timing chain/belt or jumped timing.
P0550 — P0550 — Power Steering Pressure 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, poor ground connection, control module driver fault.