The U0111 error code is an obd diagnostic trouble code DTC, indicating that the vehicle's main computer, ECU has lost communication with the Battery Energy Control Module A.
The battery energy control module, BECM
Controlling the entire Battery Energy Management System automatically ensures that your car has enough battery power to start the engine, based on the battery charge state and the temperature.
The BECM monitors the battery’s voltage level and the charging activity while driving. If necessary, it increases the idle speed slightly to enhance the alternator’s charging output. In extreme cases, very high-consumption components such as seat heating are temporarily shut down, but if you’re driving normally, this interruption is so brief that you will barely notice it.
So when the BECM loses communication with the ECM, the U0111 error code, and your car will suffer the following symptoms.
1. Illuminated Check Engine Light
When the BECM loses communication with the rest of the vehicle’s systems, the engine control unit (ECU) recognizes this fault and triggers the Check Engine Light. The ECU relies on the BECM for vital data related to the battery’s state and energy management.
2. Battery Warning Light
If the ECU can't receive data concerning battery health, due to a communication fault, it triggers the battery warning light to alert the driver of a potential issue with the battery or charging system.
3. Starting Issues
The BECM is crucial for managing the energy flow to start the vehicle. If there’s no communication, the vehicle might not receive the necessary signals to start properly, leading to delayed start, difficulty starting, or even failure to start. When this poorly diagnosed, the mechanic may erroneously blame this on bad kick starter, starter button, or even dead battery where as non of this is actually the cause.
4. Performance Issues
The BECM also plays a significant role in managing the vehicle’s energy efficiency and performance. Without communication from the BECM, the ECU might enter a default or limp mode to protect the vehicle, resulting in reduced power, poor acceleration, or stalling.
5. Charging Problems
The BECM ensures that the battery is charging correctly by controlling the alternator output and monitoring the battery's health to avoid over charging, thereby destroying the battery cells. A communication failure means that the charging system might not function properly, leading to undercharging or overcharging the battery. If you have had that case where you are advised to change the alternator and you did but the battery charging issues continued, here is your culprit.
6. Electrical Problems
The BECM’s role in energy management extends to various electrical systems in the vehicle. A lack of communication can cause erratic behavior in other systems, such as lights flickering, infotainment malfunctions, or other electrical accessories not working correctly.
In this video we will go ahead to discuss the causes of this problem and very simple solutions you can perform from anywhere.