What it means
The brake control module checks whether the master cylinder piston position sensor calibration has been learned. It sets this code when the required calibration value is missing or invalid.
At a glance
- Usually lights the ABS or stability-control warning light
How it works
The brake control module needs a learned calibration value for the master-cylinder piston-position sensor to interpret its readings correctly. This code sets when that value is missing or invalid, commonly after service or an interrupted setup.
Common causes
Most likely first.
- Calibration or relearn not completed
- Sensor or master cylinder replaced without initialization
- Calibration interrupted or performed incorrectly
- Low system voltage during setup
Symptoms
- ABS warning light on
- ESC/stability control may be disabled
How to diagnose it
- Read the brake-module freeze-frame, calibration status, and related codes to confirm that the missing or invalid learned value is the active issue.
- Check system voltage and battery condition, especially if the code appeared after a low-voltage event or during setup.
- Inspect the piston-position sensor connector and wiring for damage or poor contact that could prevent calibration.
- Review recent work on the master cylinder or sensor and confirm that the correct components are installed and connected.
- Perform the required calibration or relearn using the manufacturer's procedure and verify that the learned status is accepted.
Common fixes
- Complete the required sensor calibration or relearn.
- Restore stable system voltage and repeat the setup if low voltage interrupted it.
- Repair a poor connector or damaged sensor wiring that prevents learning.
- Replace a faulty sensor or master-cylinder component only if it fails the manufacturer's checks.
Can I keep driving?
If braking feels normal, a short cautious trip for repair may be possible, but ABS or stability control may be limited. Avoid hard braking and slippery conditions until the calibration is learned and the warning clears.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.