U0656 indicates the Powertrain Control Module (PCM) has lost communication with the turbocharger/supercharger boost control position sensor, which monitors boost pressure for proper engine operation.
The sensor itself may have failed electrically or mechanically, preventing it from sending a valid signal to the PCM.
Broken, frayed, or corroded wires or connectors in the sensor circuit can interrupt communication.
A connector that is not fully seated or has bent pins can cause intermittent signal loss.
A fuse that supplies power to the sensor circuit may be open, cutting power to the sensor.
Only after ruling out sensor, wiring, and fuse issues should a PCM internal fault be considered, which is uncommon.
In most cases no. The PCM is rarely at fault for this code; it is far more common that the sensor, wiring, or fuse is the problem.
Yes. The boost control sensor circuit is protected by a fuse; if that fuse is open, the sensor will lose power and communication will be lost.
Clearing the code may temporarily turn off the Check Engine Light, but if the underlying issue remains, the code will reappear on the next drive cycle.
The vehicle will operate in a default or limp mode with reduced boost, which limits performance but generally allows the car to be driven to a safe location for repair.