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

• U0227 — OBD2 code U0227 flags a problem with the vehicle network (CAN bus) communication (lost communication with "door window motor F"). 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.
• U0228 — U0228 — Lost Communication With "Door Window Motor G". 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, water ingress in harness junctions.
• U0229 — U0229 — Lost Communication With Heated Steering Wheel Module. 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, damaged CAN bus wiring or short to power/ground, corroded connectors, especially in wet areas.
• U0230 — OBD2 code U0230 flags a problem with the vehicle network (CAN bus) communication (lost communication with rear gate module). Short, gentle driving to a shop is usually possible. Common culprits: corroded connectors, especially in wet areas, aftermarket equipment interfering with the bus, damaged CAN bus wiring or short to power/ground.
• U0231 — U0231 — Lost Communication With Rain Sensing 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, aftermarket equipment interfering with the bus, corroded connectors, especially in wet areas.
• U0232 — U0232 — Lost Communication With Left Side Obstacle Detection 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, poor grounds or low battery voltage, a faulty module pulling the bus down.
• U0233 — OBD2 code U0233 flags a problem with the vehicle network (CAN bus) communication (lost communication with right side obstacle detection control module). Short, gentle driving to a shop is usually possible. Common culprits: poor grounds or low battery voltage, water ingress in harness junctions, damaged CAN bus wiring or short to power/ground.
• U0234 — Lost Communication With Convenience Recall Module (U0234): 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, a faulty module pulling the bus down, damaged CAN bus wiring or short to power/ground.
• U0235 — OBD2 code U0235 flags a problem with the vehicle network (CAN bus) communication (lost communication with cruise control front distance range sensor). Short, gentle driving to a shop is usually possible. Common culprits: aftermarket equipment interfering with the bus, water ingress in harness junctions, a faulty module pulling the bus down.
• U0236 — Lost Communication With Column Lock Module (U0236): 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, poor grounds or low battery voltage, damaged CAN bus wiring or short to power/ground.
• U0237 — Lost Communication With "Digital Audio Control Module C" (U0237): 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, water ingress in harness junctions.
• U0238 — Lost Communication With "Digital Audio Control Module D" (U0238): 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, water ingress in harness junctions, corroded connectors, especially in wet areas.
• U0239 — OBD2 code U0239 flags a problem with the vehicle network (CAN bus) communication (lost communication with entrapment control module "A"). Short, gentle driving to a shop is usually possible. Common culprits: damaged CAN bus wiring or short to power/ground, aftermarket equipment interfering with the bus, corroded connectors, especially in wet areas.
• U023A — U023A — Lost Communication With Image Processing Module "A". 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, corroded connectors, especially in wet areas, a faulty module pulling the bus down.
• U023B — OBD2 code U023B flags a problem with the vehicle network (CAN bus) communication (lost communication with image processing 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.
• U023C — U023C — Lost Communication With Image Processing 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, a faulty module pulling the bus down, water ingress in harness junctions.
• U023D — Lost Communication With Cruise Control Front Distance Range Sensor Left (U023D): 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, corroded connectors, especially in wet areas.
• U023E — U023E — Lost Communication With Cruise Control Front Distance Range Sensor Right. 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, a faulty module pulling the bus down, corroded connectors, especially in wet areas.
• U0240 — Lost Communication With Entrapment Control Module "B" (U0240): 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.
• U0241 — U0241 — Lost Communication With Headlamp Control Module "A". 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, water ingress in harness junctions, corroded connectors, especially in wet areas.
• U0242 — OBD2 code U0242 flags a problem with the vehicle network (CAN bus) communication (lost communication with headlamp 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, aftermarket equipment interfering with the bus.
• U0243 — OBD2 code U0243 flags a problem with the vehicle network (CAN bus) communication (lost communication with parking assist control module "B"). Short, gentle driving to a shop is usually possible. Common culprits: water ingress in harness junctions, poor grounds or low battery voltage, damaged CAN bus wiring or short to power/ground.
• U0245 — U0245 — Lost Communication With Entertainment Control Module Front. 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, poor grounds or low battery voltage, a faulty module pulling the bus down.
• U0246 — U0246 — Lost Communication With "Seat Control Module E". 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, corroded connectors, especially in wet areas.