IBST family
IBST_a026_ecuBistCmdTestFault
Power braking assist reduced
What does the IBST_a026_ecuBistCmdTestFault alert mean?
iBooster (IBST) has detected (contrary to specifications) the Built-In Self-Test (BIST) state machine of system Integrated Circuit (IC) is started by an incorrect BIST command.
What you'll see in your Tesla
- Power braking assist reduced
- Braking may require increased effort
What triggers it
IBST detects the BIST state machine of system IC is started by an incorrect BIST command.
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.