U0111 on Mercedes-Benz: How to Diagnose & Fix
Lost Communication With Battery Energy Control Module "A"
3 Mercedes-Benz models · 3 documented issues · 2 critical
U0111 on Mercedes-Benz by model: symptoms, diagnosis and fix
The facelifted GLB (2024 onward) gained a 48-volt mild-hybrid system with a second-generation belt-driven starter-generator (RSG), so the car now depends on a small 48V lithium-ion battery for engine restarts, coasting, and recuperation in addition to the conventional 12V battery. Owners on the MBWorld GLB forum report repeated 12V battery discharge - dead or weak battery after short periods parked, requiring frequent jump starts or a tender. Mercedes-Benz opened service campaign 2025100004 (late October 2025) to update the 48-volt on-board electrical system battery software, because a communication error can occur when the 48V lithium-ion battery is reactivated during reinitialization; the same campaign covers CLA and GLA. Per the campaign bulletin, the system can store this error and illuminate the check engine (malfunction indicator) lamp unnecessarily; the bulletin does not link it to 12V battery drain. Separately, GLB owners across model years report the small 1.2 Ah auxiliary battery plus short-trip driving leaves the 12V battery chronically undercharged.
Common Symptoms
- Check engine light illuminated with a stored 48V battery communication fault
- 12V battery flat after the car sits a few days
- Repeated jump starts needed
- Electrical system warning messages on startup
- Stop/start and coasting functions unavailable
- Car needs more frequent driving than normal to stay charged
How to Fix
Have the dealer check the VIN against service campaign 2025100004 and flash the updated 48V battery control software - it is a free software update, not a battery replacement. If discharge continues afterward, have a proper parasitic-draw test performed with the vehicle fully asleep (Mercedes modules can take 20-40 minutes to shut down, so a quick draw test gives a false result). Replace the 12V battery only after the campaign and the draw test, and always register/code the new battery with Xentry - an unregistered battery is undercharged by the charging strategy and will fail again. A CTEK-type maintainer is a reasonable stopgap for garage-kept cars.
Call to confirm they can assess your vehicle and perform the stated work. Search results do not confirm qualification, eligibility or coverage.
Sources for this issue (6)
- Mercedes-Benz Service Campaign 2025100004 - Update 48-V On-Board Electrical System Battery Software (CLA, GLA/GLB, MY2024-2026)manufacturer
- GLB 48-V Battery Service Campaign 10-31-25 - MBWorld.org GLB Class (X247) forumforum
- Auxiliary battery - MBWorld.org GLB Class (X247) forumforum
- BATTERY - MBWorld.org GLB Class (X247) forumforum
- More features and improved technology for Mercedes-AMG GLA and GLB (MBUSA media release - 48V RSG mild hybrid)article
- More features and improved technology for Mercedes-AMG GLA and GLB (Mercedes-Benz Canada media release)article
Other control units on the EVA2 platform continuously send diagnostic requests to the high-voltage battery management system (BMS). The BMS memory capacity overflows, the module shuts down and commands the HV contactors open, disconnecting the 90.6 kWh pack from the drive unit. The car loses propulsion without warning while driving; steering and brakes remain but power assist behavior changes. NHTSA campaign 24V-372 covers 14,912 EQE/EQS vehicles built roughly Feb 1 2023 - May 11 2024.
Common Symptoms
- Sudden loss of drive power while driving
- No warning before the loss of propulsion
- Vehicle coasts to a stop in traffic
- Car can be restarted once stopped
How to Fix
Dealer reflash of the battery management system control unit under recall 24V-372 (MBUSA recall number 2024060002). This remedy is NOT deliverable over the air — the car must go to a Mercedes dealer for a XENTRY flash. If the car has already lost drive power, the recall report states it can be restarted once it comes to a standstill, but the software update is the permanent fix. Check VIN at nhtsa.gov/recalls.
Sources for this issue (3)
Other control units on the EVA2 bus continuously send diagnostic requests to the high-voltage battery management system. The BMS memory overflows, the module shuts down, and the HV contactors open - disconnecting the 108 kWh pack from the drive unit. The result is an instant loss of propulsion at speed with the red turtle icon on the display, even with a nearly full state of charge. NHTSA recall 24V-372 covered 14,912 EQE/EQS sedans and SUVs, and owners reported the failure occurring on freeways before the fix.
Common Symptoms
- Complete loss of drive power while driving
- Red turtle warning icon on display
- "Electrical system malfunction" message
- Vehicle coasts to a stop with charge remaining in the pack
- Restart required to regain drive
How to Fix
Dealer reflashes the battery management system software under recall 24V-372 (no cost). If loss-of-power events continue after the flash, the shop should check for a weak 12V auxiliary battery and pull HV network fault memory, since a low 12V supply produces the same symptom set.
Sources for this issue (3)
U0111 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does U0111 mean on a Mercedes-Benz?
U0111 stands for "Lost Communication With Battery Energy Control Module "A"." Sets when a module loses data-bus communication with Battery Energy Control Module 'A' (the high-voltage battery management controller) and no longer receives its expected messages. On Mercedes-Benz it is documented across 3 models: GLB, EQE, EQS SUV.
What are the most common causes of U0111?
The most common causes of U0111 are: Open or shorted bus wiring to the battery energy control module, Corroded or loose connector / poor ground, Blown fuse / lost low-voltage power feed, Low 12V battery voltage, Failed battery energy control module. The specific cause varies by vehicle.
How much does it cost to fix U0111 on a Mercedes-Benz?
Repair costs vary widely with the root cause and Mercedes-Benz model; each issue on this page carries its own estimate where one is published.
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Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.