Failed or internally shorted battery monitor module; Corroded, loose, or disconnected electrical connector at the battery monitor module; Damaged or chafed wiring in the controller area network bus circuit between the battery monitor module and the gateway or engine control module; Blown fuse or poor ground connection serving the battery monitor module; Software or calibration issue in the battery monitor module or gateway module requiring reprogramming; Water intrusion or physical damage to the battery monitor module, often from a leaking battery or engine compartment wash; Controller area network bus fault elsewhere that disrupts communication with multiple modules, though U01B0 alone points to the battery monitor module

DTC codes / U01xx · Lost communication with a control module / U01B0

U01B0Lost Communication With Battery Monitor Module

Q: What does code U01B0 mean?

Lost Communication With Battery Monitor Module. U01B0 is a generic network communication code indicating that the engine control module or another primary module has lost contact with the battery monitor module over the vehicle's controller area network bus. The computer has detected that expected periodic messages from the battery monitor module are no longer arriving, which can disable battery state-of-charge reporting and energy management features.

U01B0 is a generic network communication code indicating that the engine control module or another primary module has lost contact with the battery monitor module over the vehicle's controller area network bus. The computer has detected that expected periodic messages from the battery monitor module are no longer arriving, which can disable battery state-of-charge reporting and energy management features.

SystemNetwork

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaLost communication with a control module

Symptoms you may notice

Illumination of the check engine light or a dedicated battery/charging system warning light
Often no symptoms besides the warning light, with the vehicle starting and running normally
Inaccurate or missing battery state-of-charge or voltage readings on the dashboard or infotainment display
Automatic start-stop system may become disabled or behave erratically
Charging system may default to a fixed voltage instead of smart charging, reducing fuel efficiency
In some cases, a no-start condition if the battery monitor module is part of the immobilizer or power management strategy

Common causes, most likely first

Failed or internally shorted battery monitor module
Corroded, loose, or disconnected electrical connector at the battery monitor module
Damaged or chafed wiring in the controller area network bus circuit between the battery monitor module and the gateway or engine control module
Blown fuse or poor ground connection serving the battery monitor module
Software or calibration issue in the battery monitor module or gateway module requiring reprogramming
Water intrusion or physical damage to the battery monitor module, often from a leaking battery or engine compartment wash
Controller area network bus fault elsewhere that disrupts communication with multiple modules, though U01B0 alone points to the battery monitor module

How to diagnose and fix it

Verify battery voltage and condition first, as a weak battery can cause spurious communication codes
Inspect the battery monitor module connector and terminals for corrosion, tightness, and proper seating
Check all fuses and grounds that supply power and ground to the battery monitor module
Perform a wiggle test on the wiring harness while watching live data for the battery monitor module to reveal intermittent connections
Use a scan tool to check for communication with the battery monitor module directly; if it does not respond, proceed to circuit testing
Measure resistance and continuity on the controller area network bus wires between the battery monitor module and the gateway or engine control module
If wiring and power are confirmed good, replace the battery monitor module and perform any required relearn or calibration procedure

Battery monitor faults that mimic network codes

A weak or failing 12-volt battery is a common root cause of U01B0 because low voltage during cranking can drop the battery monitor module offline and set a communication code that clears after a recharge.
Many vehicles use the battery monitor module as part of the smart charging system, so a failed module can cause the alternator to default to a constant 14-volt output, which masks the fault but reduces fuel economy.
After replacing the battery monitor module, some vehicles require a battery registration or adaptation procedure through a scan tool, and skipping this step can leave the new module non-functional or set the code again.
A controller area network bus fault at another module can sometimes prevent the battery monitor module from communicating, so always check for other communication codes before condemning the module itself.
Corrosion at the battery monitor module connector is often caused by battery acid vapors or a leaking battery case, so inspect the battery for swelling or leakage when the connector shows green or white corrosion.

Can I keep driving with U01B0?

The vehicle is generally safe to drive with U01B0 because the fault mainly affects battery monitoring and smart charging, but avoid long trips or heavy electrical loads until repaired. If the charging system warning light is also on or the battery is not being charged, stop driving and address the fault immediately to prevent a no-start condition.

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.