BMS family
BMS_a127_SW_shunt_SNA
Vehicle may not restart
What does the BMS_a127_SW_shunt_SNA alert mean?
The battery management system (BMS) has detected that the shunt is unavailable (SNA).
What you'll see in your Tesla
- Vehicle may not restart
- Service is required
What triggers it
The BMS does not receive consecutive current readings from the high voltage processor (HVP).
When it clears
The BMS receives all of the expected messages from the HVP.
Potential impact
Inability to charge, drive, or support the low voltage (LV) system
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.