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.

U0095 — OBD2 code U0095 flags a problem with the vehicle network (CAN bus) communication (U0095 - control module communication bus v off). Short, gentle driving to a shop is usually possible. Common culprits: a faulty module pulling the bus down, damaged CAN bus wiring or short to power/ground, aftermarket equipment interfering with the bus.
U0096 — U0096 — U0096 - Control Module Communication Bus W Off. A fault in the vehicle network (CAN bus) communication. Short, gentle driving to a shop is usually possible. Typical causes: a faulty module pulling the bus down, damaged CAN bus wiring or short to power/ground, poor grounds or low battery voltage.
U0097 — OBD2 code U0097 flags a problem with the vehicle network (CAN bus) communication (U0097 - control module communication bus x off). Short, gentle driving to a shop is usually possible. Common culprits: corroded connectors, especially in wet areas, aftermarket equipment interfering with the bus, poor grounds or low battery voltage.
U0098 — U0098 — U0098 - Control Module Communication Bus Y Off. A fault in the vehicle network (CAN bus) communication. Short, gentle driving to a shop is usually possible. Typical causes: water ingress in harness junctions, a faulty module pulling the bus down, poor grounds or low battery voltage.
U0099 — OBD2 code U0099 flags a problem with the vehicle network (CAN bus) communication (U0099 - control module communication bus z off). Short, gentle driving to a shop is usually possible. Common culprits: damaged CAN bus wiring or short to power/ground, poor grounds or low battery voltage, a faulty module pulling the bus down.
U0103 — Lost Communication With Gear Shift Module (U0103): a vehicle network fault affecting the automatic transmission control. Short, gentle driving to a shop is usually possible. Most often caused by low or degraded transmission fluid, wiring or connector faults in the valve body harness, internal mechanical wear (clutches, torque converter).
U0104 — OBD2 code U0104 flags a problem with the vehicle network (CAN bus) communication (lost communication with cruise 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.
U0105 — U0105 — Lost Communication With Fuel Injector 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, clogged or leaking fuel injectors, contaminated or incorrect fuel.
U0107 — OBD2 code U0107 flags a problem with the throttle and intake air metering (lost communication with throttle actuator control module). Short, gentle driving to a shop is usually possible. Common culprits: wiring or connector faults in the throttle circuit, failed electronic throttle motor, faulty throttle position sensor or pedal sensor.
U0108 — OBD2 code U0108 flags a problem with the vehicle network (CAN bus) communication (lost communication with alternative fuel control module). Short, gentle driving to a shop is usually possible. Common culprits: corroded connectors, especially in wet areas, poor grounds or low battery voltage, damaged CAN bus wiring or short to power/ground.
U0109 — U0109 — Lost Communication 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: vacuum or intake leaks skewing the mixture, faulty fuel rail pressure sensor or wiring, faulty fuel pressure regulator.
U010A — Lost Communication With Exhaust Gas Recirculation Control Module "A" (U010A): a vehicle network fault affecting the exhaust gas recirculation (EGR) system. The car is usually drivable while you plan the repair. Most often caused by faulty EGR solenoid or wiring, vacuum leaks in EGR control lines, carbon buildup blocking the EGR valve or passages.
U010C — Lost Communication With Turbocharger/Supercharger Control Module "A" (U010C): a vehicle network fault affecting the turbocharger / supercharger boost control. Short, gentle driving to a shop is usually possible. Most often caused by stuck wastegate or faulty boost control solenoid, worn turbocharger, vacuum or actuator line damage.
U010D — Lost Communication With Turbocharger/Supercharger Control Module "B" (U010D): a vehicle network fault affecting the turbocharger / supercharger boost control. Short, gentle driving to a shop is usually possible. Most often caused by faulty boost pressure sensor, stuck wastegate or faulty boost control solenoid, worn turbocharger.
U0112 — U0112 — Lost Communication With Battery Energy Control Module "B". A fault in the vehicle network (CAN bus) communication. Short, gentle driving to a shop is usually possible. Typical causes: poor grounds or low battery voltage, a faulty module pulling the bus down, water ingress in harness junctions.
U0113 — Lost Communication With Emissions Critical Control Information (U0113): 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, a faulty module pulling the bus down, water ingress in harness junctions.
U0116 — Lost Communication With Coolant Temperature Control Module (U0116): a vehicle network fault affecting the engine cooling and temperature control. Short, gentle driving to a shop is usually possible. Most often caused by faulty coolant temperature sensor, wiring faults in the sensor circuit, thermostat stuck open or closed.
U0117 — OBD2 code U0117 flags a problem with the vehicle network (CAN bus) communication (lost communication with PTO control module). Short, gentle driving to a shop is usually possible. Common culprits: corroded connectors, especially in wet areas, poor grounds or low battery voltage, aftermarket equipment interfering with the bus.
U0118 — Lost Communication With Fuel Additive Control Module (U0118): a vehicle network fault affecting the vehicle network (CAN bus) communication. Short, gentle driving to a shop is usually possible. Most often caused by poor grounds or low battery voltage, aftermarket equipment interfering with the bus, a faulty module pulling the bus down.
U0119 — OBD2 code U0119 flags a problem with the vehicle network (CAN bus) communication (lost communication with fuel cell control module). Short, gentle driving to a shop is usually possible. Common culprits: corroded connectors, especially in wet areas, water ingress in harness junctions, damaged CAN bus wiring or short to power/ground.
U011B — Lost Communication With Rocker Arm Control Module "A" (U011B): 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, poor grounds or low battery voltage.
U011C — OBD2 code U011C flags a problem with the vehicle network (CAN bus) communication (lost communication with rocker arm control module "B"). Short, gentle driving to a shop is usually possible. Common culprits: aftermarket equipment interfering with the bus, water ingress in harness junctions, damaged CAN bus wiring or short to power/ground.
U011D — U011D — Lost Communication With All Wheel Drive Control Module. A fault in the vehicle network (CAN bus) communication. Short, gentle driving to a shop is usually possible. Typical causes: a faulty module pulling the bus down, damaged CAN bus wiring or short to power/ground, water ingress in harness junctions.
U0123 — Lost Communication With Yaw Rate Sensor Module (U0123): 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, damaged tone (reluctor) ring on the hub.