U0111–U0112 Lost Communication With Battery Energy Control Module A
This module has stopped talking on the car's data network, so nothing else can hear it.
Can you drive it? The engine light will stay on and the car may run in a reduced-power mode. Read the freeze-frame data to see the conditions the fault was logged under.
Which code is which
Same fault, different cylinder or bank — diagnosed the same way. Several set together usually means one shared cause.
| Code | Definition | Severity |
|---|---|---|
U0111 | Lost Communication With Battery Energy Control Module A | Investigate soon |
U0112 | Lost Communication With Battery Energy Control Module B | Investigate soon |
The definition
U0111: Lost Communication With Battery Energy Control Module A.
U0111 is a network code (communication between control modules), defined by the SAE standard - it means the same thing on any make of car, and any generic OBD-II reader will decode it.
What to check first
Cheapest and fastest checks first:
- Check power and earth at the module first - a module with no supply cannot answer.
- Check the two data-bus wires for continuity and for a short between them.
- Scan the other modules: if several report the same module missing, the fault is at that module rather than on the bus.
What actually causes this on a VAG
Read this one carefully, because it is easy to end up at completely the wrong end of the car. The official definition is "Lost Communication With Battery Energy Control Module A", and it sits in the block of codes that covers electrified drivetrains - the code immediately before it is for the drive motor control module, and the one immediately after is the second battery energy control module. In VAG's own tables it points at the battery regulation control module: the unit that manages a high-voltage or 48-volt battery on a hybrid, plug-in hybrid, mild hybrid or electric model. It is not the small sensor clamped to the 12-volt battery's negative terminal. That is a different part - the battery monitoring control module, the one that feeds start-stop and charging strategy - and it reports over a different connection and logs different faults. If your car has no electrified drivetrain at all, be sceptical of this code before spending anything on it, and get it confirmed with a tool that reads VAG's own fault text and tells you which module stored it. Treat this as a job for a qualified technician. A high-voltage battery stores enough energy to kill, the orange cabling is not something to unplug, probe or work around, and a battery management module that has gone silent is exactly the situation where you cannot assume the system has shut down safely. Expect reduced power, no electric drive, no charging, or a refusal to start, with a warning on the dash.
Most likely causes, in order
- A weak or flat 12-volt battery. The cheapest thing to rule out, and safe for an owner to have checked. Even on a hybrid or an electric car, the modules that talk to each other run off the ordinary 12-volt system. When that sags, modules reset and log lost-communication faults against one another. Have the 12-volt battery and its charging tested first - on many of these cars it is a small battery leading a hard life.
- Recent work, a jump start or a battery disconnect. A fault stored at the moment power was interrupted looks identical to a live one until you check. Find out whether it is current or stored history, and what was last done to the car, before anyone starts quoting.
- Low-voltage wiring, connectors, fuses and earths at the module. The module's own supply and data connections are ordinary low-voltage wiring, but they sit on or next to a high-voltage assembly. That makes this a workshop inspection with the correct isolation procedure, not a driveway one - the check is cheap, the access is not something to improvise.
- A genuine fault in the battery management module or the pack. Real, and the expensive end. It is established with manufacturer-level diagnostics and pack data, never by swapping parts to see what happens. Do not accept a quote for a high-voltage battery on the strength of a lost-communication code alone - a module that cannot be heard and a battery that has failed are two different findings.
Worth knowing: Two things to hold onto. First, this is not the code for the terminal-clamp battery sensor, so don't spend your afternoon on the negative post - that part is a different module and it fails and reports differently. Second, nothing about a high-voltage battery is a driveway job. Have the car read properly, establish whether the fault is current or stored, and let someone with the right equipment and isolation procedure near anything orange. Separately, and this is worth knowing whatever the outcome: when the 12-volt battery is replaced on one of these cars it normally has to be registered to the vehicle with a diagnostic tool so the charging strategy matches the battery that is actually fitted.
Reading the code is the easy part
A code names the circuit that complained. What tells you why is watching the sensor behind it while the engine runs — and that is where a code reader stops and a diagnostic tool starts.
VAGPULSE reads every module in a VW, Audi, Skoda or SEAT — not just the engine — shows the live measuring blocks behind this fault, gives you the freeze-frame conditions it was logged under, and clears it once you have fixed it. It also does what a generic OBD reader cannot on a VAG: service resets, coding, adaptations, and Stage 1–3 flashing with your original file saved first.
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Common questions
What does U0111 mean?
U0111 means Lost Communication With Battery Energy Control Module A. This module has stopped talking on the car's data network, so nothing else can hear it.
Can I drive with U0111?
The engine light will stay on and the car may run in a reduced-power mode. Read the freeze-frame data to see the conditions the fault was logged under.