C0581 code meaning
Brake Booster Motor A Phase U-V-W Circuit High
What C0581 means
C0581 is reserved for a phase of booster motor A whose voltage sits too high – typically a phase lead touching battery positive or an upper power transistor that stays conductive. No manufacturer publishes C0581: GM's brake tables list only C057F, C0580 and C0582 for the phase circuits of this motor, and its 2019 IBC unit books stuck-high phases under C057F. How such a fault is detected is laid out in gate-driver data sheets: TI's DRV8343-Q1 runs an offline short-to-supply test while the bridge is off, and the DRV3245Q-Q1, intended for electric brake and brake assist, watches drain-source voltages and phase comparators. Because a stuck upper transistor can lock the motor, the module turns assist off; the hydraulic base brake stays available.
C0581 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyHard
- Typical labor1 to 4 hours
- Clears after repairWhen cleared with a scanner
Symptoms of C0581
- Brake assist switched off, high pedal effort
- Brake system warning lamp and service message
Common causes of C0581
- Most likelyUpper bridge transistor in the brake module shorted or stuck on
- PossiblePhase lead of motor A shorted to battery voltage
- Less likelyMoisture in the booster connector creating a leakage path to supply
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Brake booster motor aMotor phase wiring
What each part of C0581 means
| C | Chassis system: brakes, ABS, steering and suspension. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 81 | The exact fault in that area. |
What to do next
- Note C0581 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about C0581
What does C0581 mean?
C0581 means "Brake Booster Motor A Phase U-V-W Circuit High". C0581 is reserved for a phase of booster motor A whose voltage sits too high – typically a phase lead touching battery positive or an upper power transistor that stays conductive. It is a generic code, so it means the same on every make.
Is it safe to drive with C0581?
Drive gently and only to a workshop. With C0581 the car can go into limp mode (reduced power) to protect itself.
Will C0581 fail an emissions test?
C0581 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is C0581 to fix?
Difficulty: hard. A typical repair takes 1 to 4 hours of work. This is a job for a workshop.
Will C0581 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.