# Service bulletin LI54.21\-P\-078926

A bulletin is a manufacturer's communication to its dealers, as NHTSA indexes it. The summary is NHTSA's. The document is the manufacturer's: read it at NHTSA. A bulletin is not a recall, and listing a model year does not mean every vehicle of it is concerned.

- Type: Service bulletin
- NHTSA id: 11021897
- Published by NHTSA: 2025\-08\-15
- Manufacturer's number: LI54.21\-P\-078926
- Manufacturer's date: 2025\-08\-04
- NHTSA component: ENGINE

## NHTSA's 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' \(PTCU\) control unit NOTE: Replacing parts does not remedy the problem.

## The document

- [NHTSA's copy of the document (PDF)](https://static.nhtsa.gov/odi/tsbs/2025/MC-11021897-0001.pdf)
- [If that address does not open, try this one](https://static.nhtsa.gov/odi/tsbs/2025/MC-11021897-9999.pdf)

The document is the manufacturer's. This site does not hold it.

## Components

Engine

## Vehicles listed

- 2020 to 2024 MERCEDES\-BENZ AMG CLA35
- 2020 to 2024 MERCEDES\-BENZ AMG CLA45
- 2021 to 2023 MERCEDES\-BENZ AMG GLA45
- 2021 to 2025 MERCEDES\-BENZ AMG GLB35
- 2020 to 2025 MERCEDES\-BENZ CLA 250
- 2021 to 2025 MERCEDES\-BENZ GLA 250
- 2024 MERCEDES\-BENZ GLA 250 4MATIC
- 2020 to 2025 MERCEDES\-BENZ GLB 250

JSON: [/v1/bulletins/11021897](/v1/bulletins/11021897)

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