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

• U3077 — U3077 — U3077 - Module Internal Data Error. 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, aftermarket equipment interfering with the bus.
• U3078 — OBD2 code U3078 flags a problem with the vehicle network (CAN bus) communication (U3078 - module internal checksum error). Short, gentle driving to a shop is usually possible. Common culprits: damaged CAN bus wiring or short to power/ground, water ingress in harness junctions, corroded connectors, especially in wet areas.
• U3079 — OBD2 code U3079 flags a problem with the vehicle network (CAN bus) communication (U3079 - module internal CRC error). 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, corroded connectors, especially in wet areas.
• U3080 — U3080 — U3080 - Module Internal Parity Error. 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, corroded connectors, especially in wet areas, damaged CAN bus wiring or short to power/ground.
• U3081 — U3081 — U3081 - Module Internal Framing Error. 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, damaged CAN bus wiring or short to power/ground, poor grounds or low battery voltage.
• U3082 — OBD2 code U3082 flags a problem with the vehicle network (CAN bus) communication (U3082 - module internal overrun error). Short, gentle driving to a shop is usually possible. Common culprits: poor grounds or low battery voltage, corroded connectors, especially in wet areas, damaged CAN bus wiring or short to power/ground.
• U3083 — U3083 - Module Internal Underrun Error (U3083): a vehicle 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.
• U3084 — U3084 - Module Internal Buffer Overflow (U3084): a vehicle 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, aftermarket equipment interfering with the bus, damaged CAN bus wiring or short to power/ground.
• U3085 — U3085 — U3085 - Module Internal Stack Overflow. 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, aftermarket equipment interfering with the bus, damaged CAN bus wiring or short to power/ground.
• U3086 — U3086 — U3086 - Module Internal Heap Error. 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, corroded connectors, especially in wet areas, poor grounds or low battery voltage.
• U3087 — U3087 - Module Internal Pointer Error (U3087): a vehicle 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, aftermarket equipment interfering with the bus, poor grounds or low battery voltage.
• U3089 — U3089 — U3089 - Module Internal Flag Error. 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.
• U3090 — U3090 - Module Internal Counter Error (U3090): a vehicle 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, corroded connectors, especially in wet areas, a faulty module pulling the bus down.
• U3091 — U3091 — U3091 - Module Internal State Error. 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, aftermarket equipment interfering with the bus.
• U3092 — U3092 - Module Internal Mode Error (U3092): a vehicle 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.
• U3093 — OBD2 code U3093 flags a problem with the vehicle network (CAN bus) communication (U3093 - module internal sequence error). Short, gentle driving to a shop is usually possible. Common culprits: water ingress in harness junctions, a faulty module pulling the bus down, corroded connectors, especially in wet areas.
• U3094 — U3094 — U3094 - Module Internal Timing Error. 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.
• U3095 — U3095 - Module Internal Synchronization Error (U3095): a vehicle 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, aftermarket equipment interfering with the bus.
• U3096 — OBD2 code U3096 flags a problem with the vehicle network (CAN bus) communication (U3096 - module internal arbitration error). Short, gentle driving to a shop is usually possible. Common culprits: water ingress in harness junctions, poor grounds or low battery voltage, corroded connectors, especially in wet areas.
• U3097 — U3097 - Module Internal Acknowledge Error (U3097): a vehicle 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, damaged CAN bus wiring or short to power/ground, poor grounds or low battery voltage.
• U3098 — OBD2 code U3098 flags a problem with the vehicle network (CAN bus) communication (U3098 - module internal form error). 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, water ingress in harness junctions.
• U3099 — U3099 - Module Internal Stuff Error (U3099): a vehicle 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, water ingress in harness junctions, damaged CAN bus wiring or short to power/ground.