U0112 indicates that the engine control module (ECM) or another controller has lost communication with the Battery Energy Control Module B (BECM B) over the vehicle's network. This typically points to a wiring, power, or ground fault affecting that specific module, or a failure of the BECM B itself.
Damaged, corroded, or loose wires in the controller area network (CAN) circuit connecting the Battery Energy Control Module B to the rest of the network are the most common cause.
A blown fuse, broken ground wire, or poor connection at the module can prevent it from powering up and communicating.
Internal failure of the BECM B itself, such as a shorted circuit or failed transceiver, can stop it from sending or receiving network messages.
Moisture or vibration can cause terminal fretting or corrosion, leading to intermittent or total loss of communication.
If the 12V auxiliary battery is weak or the DC-DC converter is failing, the BECM B may not have enough voltage to operate correctly.
Though rare, a failed ECM can stop polling or recognizing the BECM B. This should only be considered after all other causes are ruled out.
Yes, a low or failing auxiliary battery can drop the system voltage enough to prevent the BECM B from communicating. Always check battery health before replacing modules.
Almost never. The PCM is rarely the cause of a lost-communication code. Most often the issue is wiring, a fuse, or the BECM B itself. Replacing the PCM without proper diagnosis is a common and costly mistake.
The letter 'B' designates a specific module in a multi-module system, often the secondary or slave battery controller in hybrid/electric vehicles. The exact module location varies by make and model.
It depends. The vehicle may enter a reduced-power or limp mode, and hybrid assist may be lost. Driving short distances may be possible, but the underlying issue should be diagnosed promptly to avoid further damage or a no-start condition.