What does the code p0191 mean for a 2007 f150 5.4 engine?

The code P0191 for a 2007 Ford F-150 with a 5.4L engine indicates a problem with the fuel rail pressure sensor or its circuit. This code typically means that the fuel pressure is either too high or too low, which can lead to performance issues such as rough idling, stalling, or difficulty starting. It’s important to check the sensor, wiring, and fuel system components to diagnose and resolve the issue.