Code Definition

U0101 — Lost Communication with TCM

System: Network Communication  |  Type: Generic (OBD-II Standard)  |  Make: Toyota

About U0101

U0101 is a generic (obd-ii standard) network communication diagnostic trouble code recorded for Toyota vehicles. It belongs to the U-prefix family of codes, which covers inter-module network communication (CAN, LIN, FlexRay, or similar) faults.

Scanning & clearing: Network (U) codes report communication faults between modules. When diagnosing U-codes, checking the vehicle's CAN bus integrity, supply/ground at each module, and reading all modules for related faults is usually the first step.

Because U0101 is a generic OBD-II code, its base definition is shared across manufacturers. The specific diagnostic steps, reference values, and repair procedures can vary by vehicle, and the TaT Diagnostic Assistant includes verified procedures submitted by working technicians.

Code Information

DTC U0101 is set when the Engine Control Module (ECM) or other control modules fail to communicate with the Transmission Control Module (TCM) over the Controller Area Network (CAN) bus. This loss of communication can result in transmission performance issues, failure to shift, or the vehicle entering a fail-safe mode.

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