U01AB: Lost Communication With Hybrid/EV Battery Interface Control Module L

What does U01AB mean?

ECU lost CAN communication with hybrid/EV HV battery interface module L (BMS slave or cell-monitoring submodule).

The code tells you which monitor failed, not which part is broken. Test before replacing parts.

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

Common causes

• High Module unpowered
• Low Gateway module routing CAN messages incorrectly
• Low CAN terminating resistor (120 Ω) drifted out of spec

Likelihood is a general estimate across vehicles; your make and model may differ.