Corroded, loose, or damaged terminals at the battery interface control module connector; Open or shorted CAN bus wiring between the interface module and the main controller; Failed Hybrid/EV Battery Interface Control Module G internal circuitry; Blown fuse or poor ground connection supplying power to the interface module; Water intrusion or heat damage affecting the module or its harness; A separate low-voltage battery or charging system fault causing modules to drop offline

DTC codes / U01xx · Lost communication with a control module / U01A6

U01A6Lost Communication With Hybrid/EV Battery Interface Control Module G

U01A6 is a generic communication fault indicating that the vehicle's main control module has lost contact with the Hybrid/EV Battery Interface Control Module G over the high-speed CAN bus. The computer sets this code when it stops receiving the periodic status messages that module is programmed to broadcast, not when the battery itself has failed.

SystemNetwork

Code typeGeneric (all makes)

SeverityHigh

Fix difficultyProfessional

AreaLost communication with a control module

Symptoms you may notice

Illumination of the hybrid system warning light or service vehicle soon message
The vehicle may refuse to start or enter Ready mode, leaving you with a no-crank condition
Reduced power or limp-home mode with limited electric-only operation
The battery state-of-charge gauge may show dashes or remain frozen at its last reading
Often no symptoms besides the warning light if the fault is intermittent

Common causes, most likely first

Corroded, loose, or damaged terminals at the battery interface control module connector
Open or shorted CAN bus wiring between the interface module and the main controller
Failed Hybrid/EV Battery Interface Control Module G internal circuitry
Blown fuse or poor ground connection supplying power to the interface module
Water intrusion or heat damage affecting the module or its harness
A separate low-voltage battery or charging system fault causing modules to drop offline

How to diagnose and fix it

Connect a scan tool and record all stored codes in every module before clearing anything
Inspect the interface module connector for corrosion, pushed pins, or loose terminals and clean or repair as needed
Check the module's power and ground circuits with a multimeter, including the fuse that feeds it
Measure CAN bus resistance and voltage at the module connector to rule out an open or shorted data line
Perform a wiggle test on the harness while watching live communication status on the scan tool
If wiring and power are good, substitute a known-good module or perform a module swap with proper programming to confirm the fault
After repair, clear codes and verify the module stays online through a complete drive cycle

Why the battery module goes offline

A weak or failing 12-volt auxiliary battery is a frequent hidden cause because the interface module may brown out and stop transmitting before other modules show problems.
The code can be set by a single intermittent CAN message dropout, so a module that tests fine on the bench may still be the culprit under vibration or temperature swings.
Technicians often replace the battery interface module only to find a chafed harness behind a trim panel or near a seat bracket is the real fault.
U01A6 does not mean the high-voltage battery is defective; it only reports lost communication, and the battery pack may be perfectly healthy.
Aftermarket accessories tapped into the CAN bus or improperly installed remote starters can disrupt communication and set this code without any module failure.

Can I keep driving with U01A6?

Do not continue driving with this code because the vehicle may enter a reduced-power mode or shut down unexpectedly, and hybrid system faults can affect braking and steering assist. Have the vehicle towed to a qualified technician rather than risk a loss of power on the road.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.