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

• C1225 — OBD2 code C1225 flags a problem with the ABS / stability control (lamp brake warning output circuit short to battery). Short, gentle driving to a shop is usually possible. Common culprits: damaged sensor wiring or corroded connector, blown fuse or low voltage to the ABS module, faulty ABS module or pump motor.
• C1226 — C1226 — Lamp Brake Warning Output Circuit Short To Ground. A fault in the ABS / stability control. Short, gentle driving to a shop is usually possible. Typical causes: damaged tone (reluctor) ring on the hub, damaged sensor wiring or corroded connector, faulty ABS module or pump motor.
• C1227 — Speed Wheel Sensor LR Input Short Circuit To Battery (C1227): a chassis (brakes/steering/suspension) 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, open or shorted wiring in the circuit.
• C1228 — Speed Wheel Sensor LR Input Short Circuit To Ground (C1228): a chassis (brakes/steering/suspension) 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, control module driver fault, faulty sensor or actuator of the affected circuit.
• C1229 — C1229 — Speed Wheel Sensor Rear Center Coherency Fault. 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.
• C1230 — OBD2 code C1230 flags a problem with the sensor and actuator circuits (speed wheel sensor rear center input circuit failure). The car is usually drivable while you plan the repair. Common culprits: corroded, loose or damaged connector, control module driver fault, faulty sensor or actuator of the affected circuit.
• C1231 — Speed Wheel Sensor Rear Center Circuit Open (C1231): a chassis (brakes/steering/suspension) 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, blown fuse feeding the circuit.
• C1232 — C1232 — Speed Wheel Sensor Rear Center Input Short Circuit To Battery. 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.
• C1233 — C1233 — Speed Wheel LF Input Signal Missing. 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, open or shorted wiring in the circuit.
• C1234 — C1234 — Speed Wheel RF Input Signal Missing. 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.
• C1235 — C1235 — Speed Wheel RR Input Signal Missing. A fault in the sensor and actuator circuits. The car is usually drivable while you plan the repair. Typical causes: poor ground connection, faulty sensor or actuator of the affected circuit, corroded, loose or damaged connector.
• C1236 — Speed Wheel LR Input Signal Missing (C1236): a chassis (brakes/steering/suspension) 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, faulty sensor or actuator of the affected circuit.
• C1237 — Speed Wheel Rear Input Signal Missing (C1237): a chassis (brakes/steering/suspension) 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, blown fuse feeding the circuit.
• C1238 — ABS Hydraulic Pressure Differential Switch Input Circuit Failure (C1238): a chassis (brakes/steering/suspension) fault affecting the ABS / stability control. Short, gentle driving to a shop is usually possible. Most often caused by damaged tone (reluctor) ring on the hub, blown fuse or low voltage to the ABS module, damaged sensor wiring or corroded connector.
• C1239 — ABS Hydraulic Pressure Differential Switch Input Open Circuit (C1239): a chassis (brakes/steering/suspension) fault affecting the ABS / stability control. Short, gentle driving to a shop is usually possible. Most often caused by blown fuse or low voltage to the ABS module, failed wheel speed sensor, faulty ABS module or pump motor.
• C1240 — OBD2 code C1240 flags a problem with the ABS / stability control (ABS hydraulic pressure differential switch input short circuit to battery). Short, gentle driving to a shop is usually possible. Common culprits: blown fuse or low voltage to the ABS module, damaged sensor wiring or corroded connector, damaged tone (reluctor) ring on the hub.
• C1241 — C1241 — ABS Hydraulic Pressure Differential Switch Input Short Circuit To Ground. A fault in the ABS / stability control. Short, gentle driving to a shop is usually possible. Typical causes: damaged sensor wiring or corroded connector, damaged tone (reluctor) ring on the hub, faulty ABS module or pump motor.
• C1242 — ABS Outlet Valve Coil LR Circuit Failure (C1242): a chassis (brakes/steering/suspension) fault affecting the ignition system. Short, gentle driving to a shop is usually possible. Most often caused by failed ignition coil or coil pack, moisture or oil in the spark plug wells, faulty ignition control circuit in the ECM.
• C1243 — C1243 — ABS Outlet Valve Coil LR Circuit Open. A fault in the ignition system. Short, gentle driving to a shop is usually possible. Typical causes: worn spark plugs or wrong plug gap, moisture or oil in the spark plug wells, damaged coil wiring or connector.
• C1244 — OBD2 code C1244 flags a problem with the ignition system (ABS outlet valve coil LR circuit short to battery). Short, gentle driving to a shop is usually possible. Common culprits: moisture or oil in the spark plug wells, failed ignition coil or coil pack, damaged coil wiring or connector.
• C1245 — OBD2 code C1245 flags a problem with the ignition system (ABS outlet valve coil LR circuit short to ground). Short, gentle driving to a shop is usually possible. Common culprits: worn spark plugs or wrong plug gap, faulty ignition control circuit in the ECM, moisture or oil in the spark plug wells.
• C1246 — C1246 — ABS Outlet Valve Coil RR Circuit Failure. A fault in the ignition system. Short, gentle driving to a shop is usually possible. Typical causes: moisture or oil in the spark plug wells, faulty ignition control circuit in the ECM, failed ignition coil or coil pack.
• C1247 — ABS Outlet Valve Coil RR Circuit Open (C1247): a chassis (brakes/steering/suspension) fault affecting the ignition system. Short, gentle driving to a shop is usually possible. Most often caused by worn spark plugs or wrong plug gap, failed ignition coil or coil pack, moisture or oil in the spark plug wells.
• C1248 — OBD2 code C1248 flags a problem with the ignition system (ABS outlet valve coil RR circuit short to battery). Short, gentle driving to a shop is usually possible. Common culprits: moisture or oil in the spark plug wells, worn spark plugs or wrong plug gap, failed ignition coil or coil pack.