C0587 code meaning
Brake Booster Motor A Position Sensor Circuit/Open
What C0587 means
C0587 concerns the rotor position sensor of booster motor A – a resolver, a sine/cosine magnetic sensor or a set of Hall elements that tells the controller where the rotor stands so it can commutate the windings. The code reports an open sensor circuit. No manufacturer documents it publicly: GM books position faults of this motor under C0588, C0589 and C058A, and C0587 appears in GM's older keyword list only from a different numbering. Hitachi's resolver patent shows how a break is caught: a bias placed on one winding terminal must reappear at the other, otherwise a pull-up drives the reading high. Bosch describes a fallback for a booster whose rotor sensor goes silent – the motor is run open-loop with capped speed and speed changes, so assist becomes weaker.
C0587 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyHard
- Typical labor0.5 to 4 hours
- Clears after repairWhen cleared with a scanner
Symptoms of C0587
- Electric brake assist reduced or off, hard pedal
- Brake warning lamp and message
Common causes of C0587
- Most likelyBroken signal or supply wire of the position sensor
- PossiblePushed-back or corroded pin at the sensor or module connector
- PossibleSensor element inside the booster failed, booster unit usually replaced
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Booster motor a pos sensorSensor wiring
What each part of C0587 means
| C | Chassis system: brakes, ABS, steering and suspension. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 87 | The exact fault in that area. |
What to do next
- Note C0587 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 C0587
What does C0587 mean?
C0587 means "Brake Booster Motor A Position Sensor Circuit/Open". C0587 concerns the rotor position sensor of booster motor A – a resolver, a sine/cosine magnetic sensor or a set of Hall elements that tells the controller where the rotor stands so it can commutate the windings. It is a generic code, so it means the same on every make.
Is it safe to drive with C0587?
Drive gently and only to a workshop. With C0587 the car can go into limp mode (reduced power) to protect itself.
Will C0587 fail an emissions test?
C0587 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 C0587 to fix?
Difficulty: hard. A typical repair takes 0.5 to 4 hours of work. This is a job for a workshop.
Will C0587 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.