IBST family
IBST_a027_ecuFastWdTestFault
Power braking assist reduced
What does the IBST_a027_ecuFastWdTestFault alert mean?
iBooster (IBST) detected a missing Built-In Self-Test (BIST) trigger did not electrically switch off as expected.
What you'll see in your Tesla
- Power braking assist reduced
- Braking may require increased effort
What triggers it
IBST detects BIST trigger did not switch off as expected.
When it clears
iBooster can not recover from this condition. iBooster replacement may be required.
Potential impact
IBST may not operate as expected.
Affected models
Cybertruck
Model 3 2017-2023
Model 3 2024+
Model S 2021+
Model X 2021+
Model Y
Model Y 2025+
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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.