C0566 code meaning
Brake Booster Solenoid Circuit/Open
What C0566 means
Some vacuum brake boosters carry an electrically operated valve that lets air into the working chamber without pedal input – for emergency brake assist or, on hybrids, to blend friction and regenerative braking. An Aisin patent shows the idea: when energised, the solenoid admits atmospheric pressure to an auxiliary chamber and raises boost. C0566 reports an open circuit in this solenoid's wiring or coil. Ford's 2015–2019 hybrids store the ABS fault C0022 (brake booster solenoid) and mirror it as C0566 in the hybrid powertrain module; while it is active, Ford's pump motor and valve tests are suspended. Normal pedal boost usually remains, but automatic brake assist and smooth blending are lost.
C0566 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyMedium
- Typical labor0.5 to 3 hours
- Clears after repairWhen cleared with a scanner
Symptoms of C0566
- Brake system or stability warning
- Brake assist or regenerative blending unavailable
- Pedal feel changes on hybrids
Common causes of C0566
- Most likelySolenoid connector loose, unlatched or corroded at the booster
- PossibleBroken wire between ABS module and booster solenoid
- PossibleOpen solenoid coil inside the booster
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Brake booster solenoid
What each part of C0566 means
| C | Chassis system: brakes, ABS, steering and suspension. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 66 | The exact fault in that area. |
What to do next
- Note C0566 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 C0566
What does C0566 mean?
C0566 means "Brake Booster Solenoid Circuit/Open". Some vacuum brake boosters carry an electrically operated valve that lets air into the working chamber without pedal input – for emergency brake assist or, on hybrids, to blend friction and regenerative braking. It is a generic code, so it means the same on every make.
Is it safe to drive with C0566?
Drive gently and only to a workshop. With C0566 the car can go into limp mode (reduced power) to protect itself.
Will C0566 fail an emissions test?
C0566 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 C0566 to fix?
Difficulty: medium. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will C0566 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.