U0111: Lost Communication With Battery Energy Control Module A
Do not keep driving
Do not attempt to work on this yourself. The battery this module manages runs at several hundred volts and requires trained handling — see U0110.
Expect the vehicle not to power on, or to lose drive, with a full display of warnings.
Before assuming anything expensive, get the ordinary 12 volt battery tested. It is easy to forget that a hybrid or electric car still has one, and everything in the low-voltage system — including the module that manages the main battery and the network it talks on — depends on it. A weak or flat 12 volt battery produces exactly this picture on a car whose main battery is in perfect health, and it is by a distance the most common cause. It is also the cheapest thing on the list to rule out.
What this code means
The battery energy control module has stopped being heard from. The general reasoning is at U0100, and the high-voltage warning at U0110 applies here in full.
This module manages the high-voltage battery: it measures the voltage and temperature of individual cell groups, balances them, decides how much charge and discharge the pack can safely accept, and closes the contactors that connect the pack to the rest of the vehicle.
That last function is why losing communication with it stops the vehicle rather than degrading it. The contactors are held closed under command. No command means they open, and an isolated pack means no propulsion and no charging — the correct response, since connecting several hundred volts to a system that cannot be monitored would be the genuinely dangerous alternative.
One cause is far more common than the rest and is worth checking before anything expensive is contemplated: the ordinary 12 volt battery. Everything in the low-voltage system, including this module and the network it talks on, runs from it. A hybrid or electric vehicle with a flat or failing 12 volt battery produces a spectacular display of warnings and a car that will not power on, with a perfectly healthy traction pack. The argument is P0A08's — a hybrid has no alternator in the conventional sense, and the 12 volt battery is what allows the high-voltage system to be woken at all.
Likely causes
Start here
- Low system voltage · easy
- Failed power or earth supply to the module · specialist
- Damaged data bus wiring · specialist
Less common
- Corroded or loose connector · specialist
- Faulty battery energy control module · specialist
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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