C0266 code meaning
Active Brake Booster
What C0266 means
Active brake booster faults are filed under C0266 by no maker, and the reachable J2012 lists omit the code. The number is a GM one: it shows up among PIP5094's keywords, and AA1Car words it exactly like C0265, EBCM Relay Circuit, so on GM vehicles it points to the relay that powers the ABS valves and pump rather than to a booster. The part in the title is a booster that builds pressure without the driver, either a vacuum unit with a solenoid or an electromechanical design such as Bosch's iBooster, whose motor works independently of engine vacuum and can brake on its own for assistance functions. On a vehicle with such a booster, its own maker-specific codes cover faults; with C0266, first find out which module stored it.
C0266 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 C0266
- ABS or brake warning lamp on
- Assistance functions such as automatic braking unavailable
Common causes of C0266
- PossibleOn GM vehicles fault in the brake module relay supply (fuse, contact, ground)
- Less likelyFaulty actuator or motor of an active booster
- Less likelyDamaged wiring or connector to the booster or relay
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Ebcm relayActive brake boosterBrake control module
What each part of C0266 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 C0266 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 C0266
What does C0266 mean?
C0266 means "Active Brake Booster". Active brake booster faults are filed under C0266 by no maker, and the reachable J2012 lists omit the code. It is a generic code, so it means the same on every make.
Is it safe to drive with C0266?
Drive gently and only to a workshop. With C0266 the car can go into limp mode (reduced power) to protect itself.
Will C0266 fail an emissions test?
C0266 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 C0266 to fix?
Difficulty: hard. A typical repair takes 0.5 to 4 hours of work. This is a job for a workshop.
Will C0266 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.