Code C0542 indicates that the brake control module has detected a low voltage condition in the brake pressure sensor B circuit. This sensor monitors hydraulic pressure in the braking system, and a low signal typically points to a sensor, wiring, or connector issue rather than a module failure.
The sensor itself may have an internal open circuit or degraded output causing a low voltage signal.
Chafed, cut, or corroded wires in the sensor signal circuit can pull the voltage low.
Poor contact at the sensor connector or the ABS/ESC module connector increases resistance and drops signal voltage.
The module's internal pull-up resistor or signal processing circuit may fail, but this is less common than sensor or wiring faults.
The powertrain control module rarely causes this code; it would only be considered after all other causes are eliminated.
Low brake fluid typically triggers a different code or warning; it does not directly cause a low voltage signal in the sensor circuit.
No, the PCM is almost never the cause of C0542; the fault is almost always in the sensor, wiring, or ABS/ESC module.
Base hydraulic braking usually remains functional, but ABS, stability control, and brake assist may be disabled.
The code disables advanced braking aids, so repair is recommended to restore full safety system operation.