P1757 is manufacturer-specific. In the VAG reference used here, Ross-Tech associates 18165/P1757 with an open supply-voltage circuit. Do not transfer that interpretation to another manufacturer without checking its own fault description.
Keep the power evidence with the gearbox report
A transmission warning or limp mode does not prove that the TCU has failed internally. The reference includes fuses and module wiring or connectors as well as the controller. Ask which supplies were tested and whether the fault was active during the measurements.
Record the exact gearbox and controller identification. Note any recent battery, transmission, connector or water-ingress work. If the unit communicates only intermittently, preserve the full scan from both the working and failed conditions where possible.
Avoid an incomplete replacement job
Before purchasing a donor, establish whether the original controller has the power and communication conditions it needs. A replacement can reproduce the same warning if the external fault remains. Compatibility and installation requirements are separate questions from the original diagnosis.
Send AXION the complete P1757 wording and the garage’s findings for a supported TCU assessment. Where drive selection or engagement is unpredictable, arrange suitable recovery or professional advice. Resetting adaptations is not a repair for a missing electrical supply.
Arrange an assessment
For TCU and DSG assessment, send the vehicle details and fault report to AXION. We support enquiries from drivers and garages. Workshop, postal and remote options depend on the job and are confirmed before booking.
Technical reference
Read the supporting technical documentation. The referenced design or vehicle application defines its scope; it is not a universal repair procedure.
Related reading
P189A clutch-one clearance faults on the 0AM DSG. Browse the automotive electronics repair library for other systems and symptoms.