2004 Ford F150 5.4L Engine P0191, P2196, P2198 Fault Codes - Rough Running but No Stalling
I own a 2004 Ford F150 Lariat with the 5.4L Triton engine and am currently experiencing fault codes P0191, P2196, and P2198. The truck starts reliably and runs without stalling, but occasionally exhibits rough idling. I have already replaced the Fuel Pressure Regulator (FPR) and the Fuel Pump Diaphragm Module (FPDM), and a Ford dealership inspected the wiring and confirmed that fuel pressure is within normal range. Despite these efforts, the codes persist. Given that P0191 relates to fuel pressure sensor or circuit issues, I'm concerned about potential problems such as damaged fuel rail pressure sensor, excessive resistance in the circuit, vacuum leaks, or low/absent fuel flow. I'm seeking advice on next steps for diagnosis and repair to resolve these persistent codes without further engine damage.
P0191 is typically triggered when fuel pressure is abnormal or the fuel rail pressure sensor (FRPS) circuit has a fault. Since fuel pressure readings are normal, potential causes include: a faulty FRP sensor, excessive electrical resistance in the wiring harness, vacuum leaks, or insufficient fuel delivery. Diagnostic procedures should include checking the sensor signal voltage, testing for ground faults, and verifying fuel flow under load. Refer to official Ford service manuals for P0191 troubleshooting steps.