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.

U0296 — U0296 — Lost Communication With AC to DC Converter Control Module "A". A fault in the vehicle network (CAN bus) communication. Short, gentle driving to a shop is usually possible. Typical causes: aftermarket equipment interfering with the bus, poor grounds or low battery voltage, corroded connectors, especially in wet areas.
U0297 — Lost Communication With AC to DC Converter Control Module "B" (U0297): a vehicle network fault affecting the vehicle network (CAN bus) communication. Short, gentle driving to a shop is usually possible. Most often caused by a faulty module pulling the bus down, water ingress in harness junctions, damaged CAN bus wiring or short to power/ground.
U0299 — Lost Communication With DC to DC Converter Control Module "B" (U0299): a vehicle network fault affecting the vehicle network (CAN bus) communication. Short, gentle driving to a shop is usually possible. Most often caused by damaged CAN bus wiring or short to power/ground, corroded connectors, especially in wet areas, poor grounds or low battery voltage.
U029A — Lost Communication With Hybrid Battery Pack Sensor Module (U029A): a vehicle network fault affecting the vehicle network (CAN bus) communication. Short, gentle driving to a shop is usually possible. Most often caused by damaged CAN bus wiring or short to power/ground, corroded connectors, especially in wet areas, poor grounds or low battery voltage.
U029B — U029B — Lost Communication With Drive Motor Control Module "C". A fault in the vehicle network (CAN bus) communication. Short, gentle driving to a shop is usually possible. Typical causes: corroded connectors, especially in wet areas, water ingress in harness junctions, a faulty module pulling the bus down.
U029C — OBD2 code U029C flags a problem with the vehicle network (CAN bus) communication (lost communication with drive motor control module "D"). Short, gentle driving to a shop is usually possible. Common culprits: water ingress in harness junctions, aftermarket equipment interfering with the bus, poor grounds or low battery voltage.
U029E — Lost Communication With NOX Sensor "B" (U029E): a vehicle network fault affecting the vehicle network (CAN bus) communication. Short, gentle driving to a shop is usually possible. Most often caused by water ingress in harness junctions, corroded connectors, especially in wet areas, a faulty module pulling the bus down.
U0300 — Internal Control Module Software Incompatibility (U0300): a vehicle network fault affecting the vehicle network (CAN bus) communication. Short, gentle driving to a shop is usually possible. Most often caused by corroded connectors, especially in wet areas, poor grounds or low battery voltage, a faulty module pulling the bus down.
U0302 — OBD2 code U0302 flags a problem with the automatic transmission control (software incompatibility with transmission control module). Short, gentle driving to a shop is usually possible. Common culprits: failed shift or pressure control solenoid, faulty transmission speed sensor, valve body wear.
U0303 — Software Incompatibility with Transfer Case Control Module (U0303): a vehicle network fault affecting the vehicle network (CAN bus) communication. Short, gentle driving to a shop is usually possible. Most often caused by corroded connectors, especially in wet areas, water ingress in harness junctions, aftermarket equipment interfering with the bus.
U0304 — Software Incompatibility with Gear Shift Control Module (U0304): a vehicle network fault affecting the automatic transmission control. Short, gentle driving to a shop is usually possible. Most often caused by internal mechanical wear (clutches, torque converter), failed shift or pressure control solenoid, faulty transmission speed sensor.
U0305 — Software Incompatibility with Cruise Control Module (U0305): a vehicle network fault affecting the vehicle network (CAN bus) communication. Short, gentle driving to a shop is usually possible. Most often caused by a faulty module pulling the bus down, corroded connectors, especially in wet areas, water ingress in harness junctions.
U0306 — OBD2 code U0306 flags a problem with the fuel delivery and mixture control (software incompatibility with fuel injector control module). Short, gentle driving to a shop is usually possible. Common culprits: faulty fuel rail pressure sensor or wiring, contaminated or incorrect fuel, faulty fuel pressure regulator.
U0307 — OBD2 code U0307 flags a problem with the diesel glow plug system (software incompatibility with glow plug control module). The car is usually drivable while you plan the repair. Common culprits: burned-out glow plug, blown fuse in the glow plug circuit, faulty glow plug relay or control module.
U0308 — OBD2 code U0308 flags a problem with the throttle and intake air metering (software incompatibility with throttle actuator control module). Short, gentle driving to a shop is usually possible. Common culprits: failed electronic throttle motor, intake air leaks after the MAF sensor, contaminated or failed MAF/MAP sensor.
U0309 — U0309 — Software Incompatibility with Alternative Fuel Control Module. A fault in the vehicle network (CAN bus) communication. Short, gentle driving to a shop is usually possible. Typical causes: damaged CAN bus wiring or short to power/ground, corroded connectors, especially in wet areas, water ingress in harness junctions.
U0310 — U0310 — Software Incompatibility with Fuel Pump Control Module. 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.
U0311 — Software Incompatibility with Drive Motor Control Module (U0311): a vehicle network fault affecting the vehicle network (CAN bus) communication. Short, gentle driving to a shop is usually possible. Most often caused by aftermarket equipment interfering with the bus, a faulty module pulling the bus down, water ingress in harness junctions.
U0312 — U0312 — Software Incompatibility with Battery Energy Control Module A. A fault in the vehicle network (CAN bus) communication. Short, gentle driving to a shop is usually possible. Typical causes: aftermarket equipment interfering with the bus, damaged CAN bus wiring or short to power/ground, corroded connectors, especially in wet areas.
U0313 — OBD2 code U0313 flags a problem with the vehicle network (CAN bus) communication (software incompatibility with battery energy control module b). Short, gentle driving to a shop is usually possible. Common culprits: damaged CAN bus wiring or short to power/ground, a faulty module pulling the bus down, poor grounds or low battery voltage.
U0315 — Software Incompatibility with Anti-Lock Brake System Control Module (U0315): a vehicle network 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, failed wheel speed sensor, blown fuse or low voltage to the ABS module.
U0316 — OBD2 code U0316 flags a problem with the vehicle network (CAN bus) communication (software incompatibility with vehicle dynamics control module). Short, gentle driving to a shop is usually possible. Common culprits: damaged CAN bus wiring or short to power/ground, corroded connectors, especially in wet areas, a faulty module pulling the bus down.
U0317 — Software Incompatibility with Park Brake Control Module (U0317): a vehicle network 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, failed wheel speed sensor, faulty ABS module or pump motor.
U0318 — Software Incompatibility with Brake System Control Module (U0318): a vehicle network fault affecting the ABS / stability control. Short, gentle driving to a shop is usually possible. Most often caused by faulty ABS module or pump motor, damaged tone (reluctor) ring on the hub, damaged sensor wiring or corroded connector.