MERCEDES-BENZ · 2026-08-25
Complaint Customers may report one or more of the following: • Transmission malfunction message • Check engine light illuminated • Shifts into N • Concern disappears after ignition cycle When performing a quick test, the following fault code is stored in Y3/14 ‐ Transmission control for 8‐speed dual‐clutch transmission (DKG): P056300 The on‐board power supply voltage is too high. Cause An overvoltage condition is detected exclusively within the transmission control unit, storing fault P056300 once the measured voltage exceeds 16V. Remedy This LI applies if the freeze frame data for P056300 show a supply voltage between 15.75 to 16.50 volts, and no other control units report overvoltage. (figure 1) Long Term Resolution: Software resolutions have been released. Check validity and ensure…