C004C code meaning
Brake Booster Motor A Position Sensor Exceeded Learning Limit
What C004C means
Set in an electric or electro-hydraulic brake booster when the position sensor of booster motor A reports a learned reference value outside the allowed adaptation range. The brake control unit learns the rest and travel positions of the motor-driven actuator so it can meter assist precisely; if the learned value drifts beyond the calibrated window the module can no longer trust the actuator position and stores this code. It points to a worn or shifted sensor, mechanical wear in the actuator or a learning routine that ran under wrong conditions rather than a hard electrical fault. Controlled brake assist is reduced or disabled and the brake or ABS warning lamp is set; conventional braking remains. No code-specific public bulletin was confirmed; the entry follows the SAE J2012 generic definition and electro-hydraulic brake actuator design.
C004C at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyWorkshop only
- Typical labor1 to 4 hours
- Clears after repairWhen cleared with a scanner
Symptoms of C004C
- Reduced or inconsistent brake assist
- Changed brake pedal feel
- ABS or brake warning lamp on
Common causes of C004C
- Most likelyPosition sensor worn or shifted
- PossibleMechanical wear in the booster actuator
- Less likelyLearning routine ran under wrong conditions
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 sensor
What each part of C004C means
| C | Chassis system: brakes, ABS, steering and suspension. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 4C | The exact fault in that area. |
What to do next
- Note C004C 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 C004C
What does C004C mean?
C004C means "Brake Booster Motor A Position Sensor Exceeded Learning Limit". Set in an electric or electro-hydraulic brake booster when the position sensor of booster motor A reports a learned reference value outside the allowed adaptation range. It is a generic code, so it means the same on every make.
Is it safe to drive with C004C?
Drive gently and only to a workshop. With C004C the car can go into limp mode (reduced power) to protect itself.
Will C004C fail an emissions test?
C004C 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 C004C to fix?
Difficulty: workshop only. A typical repair takes 1 to 4 hours of work. This is a job for a workshop.
Will C004C clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.