OBD-II code C0588 indicates a low signal voltage detected from the brake booster motor position sensor, which monitors the position of the electric motor used in electronic (motor-driven) brake booster systems. The sensor reports the rotor/stroke position of the assist motor so the booster controller can apply the correct level of hydraulic assist. A 'low' reading means the circuit voltage has dropped below the expected range, which the controller interprets as a sensor or wiring fault.
The position sensor is often integrated into the electric brake booster assembly and is the single most common failure point for this code. Internal wear, contamination, or electrical failure inside the sensor produces a permanently low output voltage.
Chafed insulation, broken wires, corroded pins, or moisture intrusion in the harness between the booster and its controller can pull the sensor signal low. Connector pin spread or a partially seated plug is also common after brake service.
If the assist motor itself seizes, draws excessive current, or has internal wear, the sensor's feedback can fall out of its normal range and trigger the low-circuit fault before the sensor itself is bad.
Low system voltage, a weak battery, or a poor ground at the booster assembly can depress the sensor's reference voltage and produce a falsely low reading at the controller.
A stuck caliper, seized wheel cylinder, or contaminated brake fluid can hold pressure that displaces the booster's position sensor beyond its normal range, setting the code even though the sensor is electrically fine.
The booster is normally driven by a dedicated sub-controller; a fault inside that module is uncommon but can set this code. It is the least likely cause and should only be considered after the sensor, wiring, motor, and hydraulics have been ruled out.
The vehicle can usually still be driven, but power assist may be reduced or intermittent, so stopping distances can increase. Have it diagnosed promptly, and avoid driving if the brake pedal feels unusually hard.
No. C0588 is a chassis code that lives in the brake booster subsystem, not the powertrain computer. Replacing or reprogramming the PCM will not fix it; the real cause is almost always the position sensor, its wiring, the booster motor, or a hydraulic issue.
Not always. On some vehicles the position sensor is serviceable separately, but on many it is integrated into the booster assembly, so a repair commonly involves replacing the booster (or the booster/master-cylinder unit) as a whole. Proper diagnosis first prevents unnecessary parts replacement.
Yes. The electric brake booster draws substantial current, and a weak battery or marginal charging system can cause the booster's internal voltages, including the position sensor reference, to sag and set this code. Battery and charging system health should be checked early in the diagnosis.