DTC codes / Volkswagen codes / P1851
P1851 on a Volkswagen means the engine or transmission control module has stopped receiving the periodic CAN (Controller Area Network) message broadcast by the brake control module, so it cannot confirm the brakes' status. The module that set the code detected a communication timeout, not necessarily a failed brake component, and it logs the fault once the expected message fails to arrive within the allowed window.
Guidance is general and written for Volkswagen vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.
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