DTC codes / Volkswagen codes / P1785
P1785 on Volkswagen vehicles indicates that the transmission control module (TCM) has detected a short to battery voltage on the shift up/down wire circuit, which is part of the tiptronic manual shifting system. The TCM monitors the signal line from the shift lever to the transmission and expects a specific voltage range; when the wire is shorted to B+ (battery positive), the voltage stays high and the TCM sets this fault.
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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