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

• P1540 — OBD2 code P1540 flags a problem with the sensor and actuator circuits (blower fan speed circuit range/performance). The car is usually drivable while you plan the repair. Common culprits: control module driver fault, faulty sensor or actuator of the affected circuit, poor ground connection.
• P1541 — P1541 — Intake Manifold Runner Control Range Performance. P1541 can cause surge, hesitation, and reduced drivability even if the engine still runs.
• P1542 — P1542 — Primary PCN ID Circuit Fault, Dual PCM. If the engine runs normally, drive cautiously to a repair facility and avoid heavy acceleration.
• P1543 — P1543 — Engine Coolant Heater A Circuit. P1543 generally does not indicate an immediate engine failure, but it can reduce cabin heat and slow warm-up.
• P1544 — P1544 — Engine Coolant Heater B Circuit Fault. Driving may be possible if coolant temperature remains stable and there is no overheating or temperature warning, but reduced cabin heating or unreliable warm-up can occur.
• P1545 — P1545 — EGR Positive Control Circuit Open. P1545 can affect EGR operation and engine drivability.
• P1546 — P1546 — EGR Positive Voltage Supply Too Low. P1546 does not automatically require stopping the vehicle, but low EGR control voltage may cause rough idle, hesitation, poor economy, or an emissions failure.
• P1547 — P1547 — EGR Positive-Side Supply Overvoltage. P1547 can often be driven while the charging voltage remains stable and the engine runs normally, but it should not be ignored.
• P1548 — P1548 — Engine Air Filter Restriction. P1548 normally calls for prompt inspection rather than immediate shutdown.
• P1549 — Parking Brake Switch Circuit Failure (P1549): a powertrain (engine/transmission) fault affecting the ABS / stability control. Short, gentle driving to a shop is usually possible. Most often caused by damaged sensor wiring or corroded connector, blown fuse or low voltage to the ABS module, failed wheel speed sensor.
• P1550 — Intake Manifold Runner Control (Bank 1) Stuck Open (P1550): 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, blown fuse feeding the circuit, poor ground connection.
• P1551 — P1551 — Cylinder 1 Injector Circuit Malfunction. P1551 can cause an uneven running condition, reduced power, and incomplete combustion.
• P1553 — P1553 — Cylinder 3 Injector Circuit Malfunction. If the engine runs smoothly without severe misfires, P1553 can usually be handled with a short trip to a repair shop.
• P1554 — P1554 — Cylinder 4 Injector Circuit Malfunction. Avoid extended operation if P1554 is accompanied by severe misfire, loss of power, or a fuel odor.
• P1555 — P1555 — Cylinder 5 Injector Circuit Malfunction. P1555 should be investigated before extended driving because an inactive cylinder 5 injector can cause poor running, misfire, fuel odor, or stalling.
• P1556 — P1556 — Cylinder 6 Injector Circuit Malfunction. P1556 warrants prompt diagnosis because an inactive cylinder can cause poor performance, fuel odor, or stalling.
• P1557 — P1557 — Cylinder 7 Injector Circuit Malfunction. P1557 indicates that the cylinder 7 injector circuit is not operating correctly, which can cause misfire, rough idle, or power loss.
• P1558 — P1558 — Cylinder 8 Injector Circuit Malfunction. P1558 can cause a cylinder 8 misfire, poor starting, stalling, or reduced power.
• P1562 — P1562 — ECU Hold-Memory Low Voltage. P1562 identifies a low-voltage condition at the ECU hold-memory terminal.
• P1563 — P1563 — Injection Pump Module Engine-Stop Request. P1563 records an engine-stop request from the injection pump control module.
• P1564 — P1564 — Injection Pump Reduced-Fueling Request. P1564 can limit fueling and engine output.
• P1565 — P1565 — Intake Manifold Runner Control (Bank 2) Stuck Open. 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, faulty sensor or actuator of the affected circuit, open or shorted wiring in the circuit.
• P1566 — Power To A/C Clutch Circuit Overcurrent (P1566): 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, faulty sensor or actuator of the affected circuit, open or shorted wiring in the circuit.
• P1567 — P1567 — Air Bypass Valve 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, blown fuse feeding the circuit, faulty sensor or actuator of the affected circuit.