U-Code

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📖 YOUCANIC Automotive Glossary

U-codes identify communication and network faults between modules. The U prefix stands for Network/Communication. U0xxx are generic codes; U1xxx+ are manufacturer-specific. Common codes: U0100 (ECM), U0101 (TCM), U0121 (ABS), U0140 (BCM), U0151 (SRS). U-codes can also identify invalid data received, incorrect message length, or bus off conditions.

U-codes deserve priority attention because they often represent root causes triggering secondary P, B, and C codes. When a module loses communication, every dependent system may store its own DTCs — resulting in seemingly unrelated codes all stemming from one communication failure. Always investigate U-codes first. The YOUCANIC UCAN-II reads U-codes from all modules during Auto Scan for easy root cause identification.

Synonyms:
Network Code, Communication Code
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