U0111: How to Diagnose & Fix — Lost Communication With Battery Energy Control Module "A"
7 vehicles · 4 makes · $180-$600 repair
How to diagnose and fix U0111: most-reported vehicles
Ranked by owner reports. Each card gives the symptoms, how to confirm the cause, the fix, parts and sources for that vehicle.
Mercedes-Benz EQS SUV · 2023–2025
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.
Find a Mercedes-Benz dealer
Choose to share your location for this search, or enter an area below. Your search location is sent to Google to find dealers.
Open Mercedes-Benz dealer map in Google Maps ↗Call to confirm they service Mercedes-Benz vehicles and check your VIN, recall eligibility, parts availability, and appointment options.
Sources for this issue (3)
Polestar Polestar 2 · 2021–2022
A fault in the BECM microprocessor operating system causes the processor to reset while the car is in operation. The reset drops the high-voltage contactors, disconnecting the traction pack from the drive units and producing an immediate loss of propulsion with no warning. NHTSA campaign 21V110000 (Polestar R10079) covered 3,457 US 2021-2022 Polestar 2 vehicles, reported February 23, 2021, with owner letters mailed April 23, 2021. This is the battery-management-side power-loss campaign and is separate from both the front inverter capacitor tin-plating recall and the later BMS charge-limit software campaign — a single car can be open on more than one.
Common Symptoms
- Sudden total loss of drive power while driving
- 'Reduced propulsion performance' or stop-safely-now warning on the driver display
- Car will not move from a stop and shows a high-voltage system fault
- High-voltage system shuts down while 12V accessories still work
- Fault clears after a full power cycle, then recurs
How to Fix
Free recall remedy: BECM software update, delivered either over the air or by a Polestar service point. Verify by VIN at nhtsa.gov/recalls rather than assuming an OTA landed — early cars that sat on lots or had connectivity problems did not always take the update. If a car still drops the HV system after the update, the contactor assembly and the BECM itself need to be scanned; a genuine contactor or BECM hardware failure is a warranty repair under the 8-year/100,000-mile HV battery coverage.
Sources for this issue (3)
Volvo XC40 · 2021–2022
In the XC40 Recharge BEV the Battery Energy Control Module (BECM) supervises the traction pack contactors. A microprocessor fault causes the BECM to reset while driving; on reset it opens the high-voltage contactors as a fail-safe, instantly disconnecting the traction battery from the drive units. The result is an abrupt, total loss of propulsion at speed with no warning — the car coasts, power steering and brake assist remain but regen and drive are gone. This is distinct from the well-known 12V accessory-battery no-start: here the 12V system is fine and the vehicle is already moving. NHTSA campaign 21V109000 covers 2021-2022 XC40 Recharge.
Common Symptoms
- Sudden complete loss of drive power while driving
- Vehicle coasts to a stop with no propulsion
- Red 'stop safely' / propulsion system service warning
- Vehicle restores power after a full shutdown and restart
How to Fix
Free BECM software update at a Volvo dealer under recall 21V109000 (remedy available March 30, 2021). If the fault recurs after the update, the dealer should pull traction-battery fault memory — repeat contactor-open events on updated cars have been traced to a failing BECM or a high-resistance HV connector at the pack rather than software.
Find a Volvo dealer
Choose to share your location for this search, or enter an area below. Your search location is sent to Google to find dealers.
Open Volvo dealer map in Google Maps ↗Call to confirm they service Volvo vehicles and check your VIN, recall eligibility, parts availability, and appointment options.
Sources for this issue (1)
Mercedes-Benz EQE · 2023–2025
Mercedes-Benz EQS · 2022–2025
Find U0111 by make
Browse every documented model and issue for your make.
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?
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.
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?
Repair costs for U0111 range from $180 to $600, depending on the vehicle and root cause.
Which vehicles are affected by U0111?
Au7o has documented U0111 across 7 vehicle models from 4 manufacturers: Mercedes-Benz, Polestar, Volkswagen, Volvo.
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.