U0111

Universal

Lost Communication With Battery Energy Control Module A

Definition source: General OBD-II reference catalog
Definition verification: Not independently verified for display.
Time: Varies by diagnosis and vehicle | Diagnostic difficulty: Medium
Medium Severity

The vehicle's control modules are not receiving expected messages from Battery Energy Control Module A over the vehicle communication network. That module monitors or manages battery-related information, but this code alone does not prove the module has failed. Depending on the vehicle, the condition may trigger a warning or affect battery-related functions.

Report an error with this code

⚠️ Before You Begin (Safety First)

If the vehicle displays a stop or hybrid-system warning, loses power, or behaves unpredictably, pull over safely and follow the owner's manual. Do not open or probe high-voltage battery components; have high-voltage work performed by a qualified technician.

Common Symptoms

  • A battery, hybrid-system, or powertrain warning may appear if the vehicle reports that battery-related information is unavailable.
  • Depending on the vehicle, battery-related functions or vehicle operation may be limited when the module's messages are missing.
  • Other communication-related codes may appear if additional modules are affected by the same network or power issue.
  • There may be no noticeable symptoms if the communication loss is intermittent or the affected information is not currently needed.

Common Causes

  • A loose, damaged, corroded, or poorly connected wire or connector may interrupt module communication.
  • A problem with a fuse, power supply, or ground may prevent the module from operating or communicating.
  • A fault elsewhere on the vehicle communication network may interfere with messages to or from the module.
  • Low or unstable vehicle electrical voltage may disrupt module operation or network communication.
  • The module itself may have an internal fault, but the code alone does not establish that.

Diagnostic Steps

  1. Note any warning messages and changes in vehicle behavior; consult the owner's manual for instructions specific to those warnings.
  2. With the vehicle safely parked and switched off as directed by the owner's manual, visually check accessible low-voltage battery connections and wiring for looseness or visible damage. Do not touch high-voltage components.
  3. If a suitable scan tool is available, record codes from all modules before clearing them; related codes can help distinguish a module-specific issue from a wider network or voltage problem.
  4. Have a qualified technician test the module's power, ground, and communication circuits using service information for the exact vehicle.

When to Call a Professional

Scan all modules for related communication and voltage codes before clearing anything. A technician can check whether other modules also lost communication, then inspect the relevant wiring and connectors and verify the module's power, ground, and network signals using vehicle-specific service information. Confirm the fault returns before considering module replacement.

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Commonly Asked Questions

Does U0111 prove that Battery Energy Control Module A needs replacement?

No. It reports lost communication, which can result from wiring, connector, power, ground, network, or voltage problems as well as an internal module fault.

Can the vehicle have U0111 without noticeable symptoms?

Yes. An intermittent communication problem, or one that does not affect a function currently in use, may produce no obvious symptoms.

Why should other module codes be checked?

Codes in multiple modules can point to a shared power or network issue, while a code isolated to one module may help narrow the investigation. The full scan should be interpreted using vehicle-specific information.

Is it safe to inspect the battery control system at home?

Limit home checks to safe, accessible visual inspections and low-voltage connections. Do not open or probe high-voltage battery equipment; refer that work to a qualified technician.

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Previous and next available guides in database record order, across makes. Adjacent entries may share a code number and do not necessarily describe related faults.