RCU family
RCU_a005_supplyUndervoltage
Backup power braking assist unavailable
What does the RCU_a005_supplyUndervoltage alert mean?
The Redundant Control Unit (RCU) power supply voltage is too low.
What you'll see in your Tesla
- Backup power braking assist unavailable
- OK to drive - Schedule service
What triggers it
The RCU power supply voltage is lower than 9 volts for 500 milliseconds or lower than 6.5 volts for 60 milliseconds.
When it clears
The RCU power supply voltage has returned above 9.5 volts for 500 milliseconds.
Potential impact
The RCU may not be able to perform backup power braking assist.
Affected models
Model Y 2025+
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