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August 25, 2026 Service bulletin

Complaint Customers may report one or more of the following: • Transmission malfunction message • Check...

Mercedes-Benz technical service bulletin LI27.19-P-080823 for 2021-2023 Mercedes-Benz CLA250, 2021-2023 Mercedes-Benz GLA 250 and 2021-2023 Mercedes-Benz GLB 250 and others.

Bulletin number
LI27.19-P-080823
Component
Power train
Summary
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 your Xentry is updated with latest Addons before continuing: 1. Perform software update for Y3/14 ‑ Transmission control for 8‑speed dualclutch transmission (DKG) available software listed in Parts 2. Clear fault memory and perform final test drive If the customer complaint matches this LI and the software currently installed on the vehicle is not listed, please submit a TIPS case to the Powertrain inbox with the following information: ‑ Initial Quick Test w/ Freeze Frame Data ‑ DKG Control Unit Log ‑ Latest EEPROM data ‑ Screenshot of software availability

Owners of these vehicles have filed 15 complaints in the transmission category.

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