VCBATT_a402 — LV Battery Cannot Support Vehicle

Full alert identifier: VCBATT_a402_LVBatteryCannotSupportVehicle

Message shown in the car

Electrical system backup power is unavailable Vehicle will consume more energy while idle

Alert description

The vehicle controller has detected a condition where the low voltage (LV) battery is unable to support vehicle electrical systems. The vehicle is likely to shut down if high voltage (HV) battery support for vehicle electrical systems via the power conversion system (PCS) is lost, so the HV system will remain energized to continue supplying electrical power to the vehicle until the alert clears.

Potential impact

The LV battery is unable to support vehicle electrical systems. The high voltage (HV) system will remain energized to continue supplying electrical power to the vehicle while the LV battery is unavailable. This may result in greater range loss than expected, increased HV system energy consumption when the vehicle is idle, and prevent the vehicle from sleeping.

Set condition

The LV battery is disconnected or showing degraded functionality, the LV battery internal protection transistor (MOSFET) is detected open, or the reverse battery eFuse has tripped (circuit is open).

Clear condition

The vehicle controller no longer detects a condition where the LV battery is unable to support vehicle electrical systems. May include reconnecting or replacing the LV battery, the LV battery internal protection transistor (MOSFET) being detected closed, or reverse battery eFuse no longer tripped (circuit closed again).

Signals to check

Open this alert in Service Mode Plus and review the Payload tab. Use the field names below to identify the values shown by your vehicle.

Signal	Unit
LV Battery Temp `VCBATT_a402_LVBatteryTemp` 127 SNA	degC

Signal	Unit
MOS Open `VCBATT_a402_MOSOpen`	—
Battery SM State `VCBATT_a402_batterySMState`	—
Communication Disconnect LV Battery `VCBATT_a402_communicationDisconnectLVBattery`	—
Electrical Disconnect LV Battery `VCBATT_a402_electricalDisconnectLVBattery`	—
Failure To Precharge Risk `VCBATT_a402_failureToPrechargeRisk`	—
Frunk Open `VCBATT_a402_frunkOpen`	—
Reverse Battery Fault `VCBATT_a402_reverseBatteryFault`	—
Service Mode `VCBATT_a402_serviceMode`	—

Check other alerts

With Service Mode Plus enabled, open Service Alerts → All. Review the other alerts for clues to the cause of VCBATT_a402.