U0112: Lost Communication With Battery Energy Control Module B
Do not keep driving
Do not attempt to work on this yourself — the high-voltage warning at U0110 applies. Expect the vehicle not to power on or to lose drive.
Get the ordinary 12 volt battery tested first, for the reasons at U0111 — it is the commonest cause of this picture and the cheapest to eliminate.
One thing worth mentioning to a workshop: whether codes are stored for one of these modules or for both. Both usually means something shared, such as the low-voltage supply; only one usually means the fault is inside a particular section of the battery pack, which is a narrower and more useful place to start.
What this code means
The second battery energy control module has stopped being heard from. The mechanism is at U0111 and the high-voltage warning at U0110.
A second module exists because large packs are managed in sections rather than as one unit. Cell monitoring boards are distributed through the pack, each responsible for a group of cells, and they report to — or act as — separate controllers. That is a practical necessity: the sensing wires to each cell group have to be short, so the electronics go to the cells rather than the cells to the electronics.
The useful consequence is that a fault reported by one module and not the other localises the problem to a section of the pack. Both quiet points at something shared — the low-voltage supply, the bus, or the 12 volt battery covered at U0111. One quiet points inside the pack, at that section's controller, its harness or its connector.
As at U0111, the ordinary 12 volt battery is the first thing to rule out and the cheapest.
Likely causes
Start here
- Low system voltage · easy
- Damaged data bus wiring · specialist
- Corroded or loose connector · specialist
Less common
- Failed power or earth supply to the module · 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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