Component Functional Description - Fuel Tank Pressure Sensor

Functional Operation Of The Fuel Tank Pressure (Ftp) Sensor:  Since The Vacuum Hose Between The Purge Solenoid And Intake Manifold Cannot Be Checked During The Small Leak Diagnostic The Ftp Sensor Is Used To Monitor The Evap System Pressure Change During Purging To Determine If The Hose Is Disconnected Or Restricted. The Pcm Uses The Ftp Sensor For The Purge System Performance Diagnostics.  The Diagnostic Works In Two Phases

• First The Purge Solenoid Is Actuated And The Pcm Monitors The Change In The Ftp Sensor Reading Over Time. The Pcm Expects To See The Pressure/Vacuum Reading Decrease More Than A Calibrated Threshold.
• The Purge Solenoid Is Then Deactivated And The Pcm Monitors The Change Again Over Time. The Pcm Expects To See The Pressure Reading Increase More Than A Calibrated Threshold Over A Period Of Time.

If Either Diagnostic Fails The Threshold, A Fault Is Set.