Battery Management System — Software Task Stack Usage Fault
The TESLA-BMS_A046 (Tesla BMS) EV fault code means: Battery Management System — Software Task Stack Usage Fault. This is a moderate severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- moderate
- Estimated cost
- Coolant top-off DIY $10-$25. Coolant leak repair DIY $30-$80 for hoses and fluid. Coolant pump replacement $300-$600 at an independent EV shop. Thermal valve or chiller replacement $400-$1,200 at an independent shop. Tesla service center pricing typically runs 20-40% higher.
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Common Symptoms
- Alert BMS_A046 shown on the touchscreen
- The vehicle may log the alert without any change the driver notices
Probable Causes (Ranked by Likelihood)
- The vehicle reported BMS_A046. Tesla's firmware identifies this alert as "BMS_a046_SW_Task_Stack_Usage" — an internal software diagnostic inside the battery management controller, not a battery cell or pack fault. High
Frequently Asked Questions
What does BMS_A046 mean?
Battery Management System — Software Task Stack Usage Fault. Tesla's firmware identifies it as "BMS_a046_SW_Task_Stack_Usage".
Can a generic OBD2 scanner read this?
No. Tesla alerts are a manufacturer-specific system and appear in no SAE standard, so a generic OBD-II scan tool cannot read or clear them. The alert text on the touchscreen and the Tesla app are the authoritative sources.
Mechanics Guide Step-by-step diagnosis
Step-by-Step Diagnostic Procedure
Read the alert text on the touchscreen exactly as shown — Tesla's own wording is more specific than any third-party list, this page included.
Check for a Tesla service bulletin or a pending software update; a number of alerts clear on their own after an over-the-air update.
If the alert persists, request service through the Tesla app. Tesla alerts are not standard OBD-II codes and a generic scan tool will not read or clear them.
Sources 1
This page is built from documented references. Verify against your own service info before repair work.
- Tesla alert dictionary (canonical firmware alert identifiers)community-maintained dictionary, not an official manufacturer document
Commonly Affected Vehicles
- Tesla Model 3 (Long Range AWD)
- Tesla Model 3 (RWD)
- Tesla Model Y (LR AWD)
- Tesla Model Y (Performance)
- Tesla Model S (LR)
- Tesla Model X (LR)
- Tesla Cybertruck (AWD)
Related Codes
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