BMS family
BMS_a156_SW_BMB_Vref_bad
Unable to charge
What does the BMS_a156_SW_BMB_Vref_bad alert mean?
The battery management system (BMS) detects an out-of-bounds module voltage reference.
What you'll see in your Tesla
- Unable to charge
- Service is required
What triggers it
Any battery monitoring board (BMB) reference voltage has continuously deviated outside the in-bounds threshold of the nominal voltage.
When it clears
All BMB reference voltages continuously remain within the in-bounds threshold of the nominal voltage.
Potential impact
This alert is primarily informational. Other BMB voltage signals will be substituted given the reference voltage is unreliable.
Affected models
Model 3 2017-2023
Model 3 2024+
Model S 2021+
Model X 2021+
Model Y
Model Y 2025+
Track your Tesla's alerts automatically
Alerts like this reach MyTeslaMate through your car's Tesla telemetry API. MyTeslaMate logs every alert your Tesla reports and turns it into readable history and real-time notifications — hosted TeslaMate with no server to run.