Code Definition

U012D — Lost Communication With Generator Control Module

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

About U012D

U012D is a generic (obd-ii standard) network communication diagnostic trouble code. 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 U012D 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 U012D indicates lost communication with the Generator Control Module. On vehicles with managed charging, the engine or body control module communicates with the generator control electronics, often over a LIN or dedicated control circuit, to command output voltage and monitor the generator. The code sets when valid communication from the generator control function is not received within a calibrated time. The result is usually a loss of charging control, which can cause a charge warning light, a battery warning, over or under charging, and on some vehicles related charging system codes.

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