BMS family
BMS_a178_SW_Uncontrolled_Regen_PwrB
Unable to drive
What does the BMS_a178_SW_Uncontrolled_Regen_PwrB alert mean?
The battery management system (BMS) has detected an uncontrolled regen event in track mode.
What you'll see in your Tesla
- Unable to drive
- PULL OVER SAFELY
What triggers it
The BMS detects that regen power is above the maximum threshold.
When it clears
The BMS detects that regen power is within the limit threshold.
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.