C05AF code meaning
Brake Booster Motor B Current Sensor Circuit Range/Performance
What C05AF means
C05AF is the plausibility check of the current measurement on booster side B, the second motor or winding system. No manufacturer publishes it. A separate sensing chain for B is needed wherever each power module controls its own winding, as in the Hyundai Mobis dual-winding booster motor, since every module must know its phase currents to regulate torque and to judge its own health. Typical checks run at start-up, before current flows: the controller shorts the amplifier inputs (TI's DRV8343-Q1 offers a pin for this), records the zero point and rejects values outside a band. GM's counterpart for side A, C0596, additionally injects test offsets. A failed B measurement normally leads to side B being switched off and assist relying on side A, possibly with lower power.
C05AF at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyWorkshop only
- Typical labor0.5 to 4 hours
- Clears after repairWhen cleared with a scanner
Symptoms of C05AF
- Brake assist or brake system warning
- Possibly weaker assist under hard braking
Common causes of C05AF
- PossibleFaulty current sense amplifier of side B
- PossibleZero offset of side B outside its allowed band
- Less likelyDamaged shunt or solder joint in power module B
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Booster motor b current sensorBrake system control module
What each part of C05AF means
| C | Chassis system: brakes, ABS, steering and suspension. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| AF | The exact fault in that area. |
What to do next
- Note C05AF 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 C05AF
What does C05AF mean?
C05AF means "Brake Booster Motor B Current Sensor Circuit Range/Performance". C05AF is the plausibility check of the current measurement on booster side B, the second motor or winding system. It is a generic code, so it means the same on every make.
Is it safe to drive with C05AF?
Drive gently and only to a workshop. With C05AF the car can go into limp mode (reduced power) to protect itself.
Will C05AF fail an emissions test?
C05AF 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 C05AF to fix?
Difficulty: workshop only. A typical repair takes 0.5 to 4 hours of work. This is a job for a workshop.
Will C05AF clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.