What it means
The brake pedal position sensor supply voltage is below the expected range. The module may not receive a reliable pedal-position signal.
At a glance
- Usually lights the ABS or stability-control warning light
- The engine or gearbox may go into limp mode
How it works
The brake pedal position sensor supplies pedal-position information used by the brake control system. C056D indicates that the sensor’s supply voltage is too low, so the module may not be able to rely on the reported pedal position.
Common causes
Most likely first.
- Supply wire shorted to ground
- Connector pins corroded - high contact resistance
- Harness chafing through insulation
Symptoms
- Brake or stability-control warning light
- Brake-related functions may be limited
How to diagnose it
- Read brake-module freeze-frame data and live pedal-position data to confirm the fault and note whether it occurs at rest or while pressing the pedal.
- Inspect the pedal position sensor connector and nearby harness for corrosion, loose pins, or insulation worn through.
- Check the sensor supply circuit for a short to ground, especially where the harness is routed near metal edges or moving pedal parts.
- Measure supply voltage at the sensor connector and compare it with the manufacturer’s specification.
- If the supply wire and connector pass inspection, check circuit continuity and the shared reference supply for other affected sensors.
Common fixes
- Clean or repair corroded terminals at the pedal position sensor connector.
- Repair a supply wire shorted to ground or damaged by chafing.
- Repair or replace a connector that cannot maintain reliable pin contact.
- Restore the reference supply circuit if testing identifies a fault affecting multiple sensors.
Can I keep driving?
Brake or stability-control functions may be limited, and pedal-position information may be unreliable. Avoid relying on driver-assistance braking features and do not continue if normal braking is affected; arrange prompt diagnosis.
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.