What it means
Brake Booster Motor A Position Sensor Supply Circuit/Open: the circuit is open. The electric brake booster generates the braking assist; a motor or sensor fault can reduce or disable power-assisted braking. Safety-relevant.
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 position sensor for brake booster motor A provides position information to the brake control module, while its supply circuit powers the sensor. This code sets when the module detects an open in that supply circuit, so the motor A position signal may be lost. Because the electric booster provides braking assistance, the fault can reduce or disable assist.
Common causes
Most likely first.
- Supply wire open
- Pin pushed back out of connector body
- Cracked solder joint inside the module or sensor
Symptoms
- ABS warning light on
- ESC/stability control deactivated
- Possible reduced brake assist
- Speedometer may behave erratically
How to diagnose it
- Read the brake module's codes and freeze-frame data to confirm the motor A position sensor supply open and check for related booster faults.
- Inspect the motor A position sensor connector for a loose fit or a pin pushed back into its housing.
- Trace the sensor supply wire for a break, pulled section, or harness damage near the booster and connectors.
- Check supply-circuit continuity and connector terminal fit using the manufacturer's wiring diagram and procedure.
- If the external wiring is intact, test the sensor and brake control module supply connection according to the manufacturer's specification.
Common fixes
- Reconnect and secure the motor A position sensor connector.
- Repair an open in the sensor supply wire or harness.
- Restore a backed-out pin or replace a damaged terminal.
- Replace the position sensor if its internal supply path is open and the wiring is sound.
- Repair the module connection only if testing confirms it is the source of the open.
Can I keep driving?
This fault can reduce or disable power-assisted braking and may put the vehicle into a limited operating mode. Do not continue driving if the brake pedal is unusually hard or braking is reduced; arrange recovery.
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.