U01BF: Lost Communication with Battery Management Control Module

What it means

Communication with the Battery Management Control Module was not received as expected. This code does not specify the module's architecture or the communication network used.

At a glance

• Usually lights the warning light of the system that lost communication
• The engine or gearbox may go into limp mode

How it works

The Battery Management Control Module monitors and coordinates battery operation, including high-voltage battery functions on vehicles so equipped. This code sets when other modules do not receive its expected network messages; the cause may include loss of module power or an open high-voltage interlock, but the code does not identify the network architecture.

Common causes

Most likely first.

1. Module unpowered or HV interlock open
2. Gateway module routing CAN messages incorrectly
3. CAN terminating resistor (120 Ω) drifted out of spec

Symptoms

• Multiple warning lights may illuminate
• Affected modules may go into limp mode or shut down
• Specific functions inoperative depending on module
• Diagnostic tools may show communication faults

How to diagnose it

1. Record freeze-frame data and all module codes, and note any battery, hybrid, or electric-drive warnings.
2. Use a compatible scan tool to check whether the Battery Management Control Module responds and whether related battery status data is available.
3. Check the module’s low-voltage power, ground, connectors, and wiring for looseness, corrosion, damage, or water entry.
4. Have the high-voltage interlock status checked using the vehicle’s approved diagnostic procedure; do not disconnect or probe high-voltage components.
5. If power and interlock status are sound, have the network branch, gateway routing, and CAN termination tested to the manufacturer’s specification.

Common fixes

• Restore a poor low-voltage power or ground connection at the Battery Management Control Module.
• Repair damaged low-voltage wiring or connector terminals at the module.
• Correct a confirmed interlock connection fault using the vehicle’s approved service procedure.
• Correct confirmed gateway routing or CAN termination faults to the manufacturer’s specification.

Can I keep driving?

Do not continue driving if battery or hybrid warnings appear, propulsion is limited, or the vehicle behaves abnormally; battery protection or drive functions may be affected. Avoid handling high-voltage components and arrange prompt qualified diagnosis.