Mercedes-Benz AMG CLA35 2020–2025 — technical service bulletin

Bulletin LI54.21-P-078926 · NHTSA communication 11021897 · issued Aug 4, 2025

Technical service bulletin

communication type

Engine

component

2020–2025

model years

vehicle entries

Official summary

Complaint: Check engine light comes on when driving/starting the vehicle. No drivability concerns. Cause: Communication error in G1/3 - 48 V on-board electrical system battery (48 V LIB) or N127 - 'Drivetrain' control unit (PTCU)saved and/or current Remedy: Update the software for the control unit G1/3 - 48 V on-board electrical system battery (48 V LIB) : --> Remedy-SW A001902042425/12 If the fault profile still occurs with the installed software, check the wiring and the plug contacts: UG1/3 - 48 V on-board electrical system battery (48 V LIB) N83/1 - DC/DC converter (DDW) N127 - 'Drivetrain

Vehicles covered

What a TSB means. Technical service bulletins are repair guidance manufacturers send to dealers — they are not recalls, and repairs are not automatically free (warranty extensions are an exception worth checking). The full document is available via NHTSA’s vehicle lookup.