C0650 indicates that the brake control module has detected that the brake pressure sensor signal is outside its expected range or not performing correctly. This sensor measures hydraulic brake pressure and is used by stability control and brake assist systems. A range/performance fault means the signal is plausible enough to not be flagged as an open or short, but does not match expected behavior under given conditions.
The sensor itself has drifted out of calibration or internal electronics have degraded, producing an out-of-range or implausible signal. This is the most common cause for a range/performance code.
Corrosion, pin spread, chafing, or high resistance in the five-volt reference, signal, or low-reference circuits can cause the voltage to sit within range but behave incorrectly.
Air in the hydraulic system, moisture contamination, or degraded fluid can cause real pressure behavior that the module interprets as a sensor performance fault.
Rarely, the module's internal signal conditioning or A/D conversion for that channel may fail. This should only be considered after the sensor, wiring, and hydraulic system are verified.
It is a chassis/safety-system code. Base braking still works, but ABS, traction, and stability assist may be degraded or disabled until the fault is resolved.
Short distances at moderate speed are usually possible, but stability and traction control may be inactive. Have it diagnosed promptly, especially in poor weather or emergency-braking conditions.
No. C0650 is a brake-control-system code and the PCM is almost never the cause. The brake pressure sensor, its wiring, or the brake control module are the plausible culprits, with the control module itself being the least likely.
If the sensor is integrated into the hydraulic unit and the system is opened, yes — a proper bleed, sometimes a pressure or scan-tool-actuated bleed, is required to restore correct pressure readings and pedal feel.