U01BB: Lost Communication With Battery Charger Control Module B

What it means

ECU lost communication with battery charger control module B (on-board charger for HV battery on plug-in hybrids/EVs).

At a glance

• Usually lights the warning light of the system that lost communication

How it works

Battery Charger Control Module B manages or reports one on-board charger associated with charging the high-voltage battery in a plug-in hybrid or electric vehicle. This code sets when the vehicle’s network does not receive the expected messages from charger module B; it does not by itself prove that charging voltage is wrong.

Common causes

Most likely first.

1. Module unpowered
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 all module codes and freeze-frame data, and note whether the fault occurs during charging or alongside other network faults.
2. Use a compatible scan tool to check whether Battery Charger Control Module B responds and whether charger-related status data is available.
3. Check the module’s low-voltage power, ground, connectors, and wiring for damage, corrosion, looseness, or water entry.
4. Inspect the network wiring and connectors on the charger module’s communication branch for opens, shorts, or poor contact.
5. If low-voltage supply and network wiring are sound, have gateway routing and CAN termination checked against the manufacturer’s specification.

Common fixes

• Restore a loose or corroded low-voltage power or ground connection to charger module B.
• Repair damaged wiring or connector terminals on the module’s network branch.
• Correct a confirmed gateway routing or configuration fault.
• Repair or replace a CAN terminating resistor if testing finds it outside the manufacturer’s specification.

Can I keep driving?

The vehicle may still drive, but charging may be limited or unavailable depending on the system. Avoid relying on a charge session until the fault is diagnosed, and do not touch high-voltage components; use qualified service for work beyond low-voltage checks.