2009 Ford Focus P0451: Diagnosing EVAP System Pressure Sensor Fault

I believe the FTP (Fuel Tank Pressure) sensor is functioning correctly by triggering the P0451 code. Here's a detailed breakdown of my diagnostic steps: 1. I disconnected the purge valve connector and removed the hose from the fuel tank. Using a battery-powered source, I manually operated the purge valve while the engine was running and confirmed vacuum presence — which is normal. 2. The charcoal canister and its vent solenoid were removed for bench testing; both operate as expected. 3. Air was blown through all three ports of the canister, and air flow was detected from each outlet. 4. The hose between the canister and purge valve was tested with compressed air — no blockages observed. 5. Air was blown through the vent hose from the canister to the dust collector screen — clear passage confirmed. 6. The FTP sensor tube assembly was removed and visually inspected for damage or obstructions. 7. The overfill tube in the fuel fill line was checked and found to be unobstructed. I have access to freeze frame data from the last two P045-1 events, but beyond EVAP system vapor pressure, I'm unable to identify a clear root cause. Using my OBD2 scanner, I can monitor both 'commanded evap purge' and actual vapor pressure. Based on my observations, I believe that when the PCM commands a purge cycle, negative pressure (vacuum) should be present in the EVAP system — this is consistent with normal operation. Despite these checks, the code persists, leading me to suspect either a faulty FTP sensor or an intermittent issue within its circuit.