Test C: DTC P1450: Excessive Vacuum Detected In Fuel Tank: F150

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1) Check For Visual Cause Of Excessive Fuel Tank Vacuum

Check for kinks or bends in fuel vapor hoses and tubes. Inspect EVAP canister inlet port and canister vent solenoid for contamination or foreign material. If any conditions are present, repair, replace or clean as necessary and go to next step. If no conditions are present, go to next step.

2) Check For Blockage Between EVAP Test Port & EVAP Canister Vent Solenoid

Disconnect and plug EVAP return tube at intake manifold. Plug canister vent solenoid or canister vent hose. Connect evaporative emissions system leak tester to EVAP test port. Pressurize system to 14 in. H2O (3.48 kPa). Remove plug from canister vent solenoid or canister vent hose. If pressure drops immediately, go to next step. If pressure does not drop immediately, perform HISSING SOUND WHEN REMOVING FUEL CAP symptom test under EVAPORATIVE EMISSION SYSTEM TESTS in SYSTEM & COMPONENT TESTING - GASOLINE article.

3) Check Fuel Filler Cap

Connect evaporative emissions system leak tester to fuel filler pipe and install fuel filler cap. Turn ignition switch to ON position. Close canister vent solenoid. See CANISTER VENT SOLENOID CLOSING PROCEDURE . Pressurize EVAP system to 14 in. H2O (3.48 kPa). Using ultrasonic leak detector, slowly check fuel filler cap and EVAP test port. If a leak is detected, repair or replace component and repeat this step to verify repair. If no leak is detected, go to next step.

4) Check For Blockage Between EVAP Test Port & Fuel Tank

Turn ignition switch to ON position. Close canister vent solenoid. See CANISTER VENT SOLENOID CLOSING PROCEDURE . Pressurize EVAP system to 14 in. H2O (3.48 kPa). Depress the Schrader valve in the emission test port. If pressure drops immediately, go to next step. If pressure does not drop immediately, perform HISSING SOUND WHEN REMOVING FUEL CAP symptom test under EVAPORATIVE EMISSION SYSTEM TESTS in SYSTEM & COMPONENT TESTING - GASOLINE article. Connect evaporative emissions system leak tester to fuel filler pipe. Pressurize EVAP system to 14 in. H2O (3.48 kPa). If pressure drops immediately, go to next step. If pressure does not drop immediately, perform HISSING SOUND WHEN REMOVING FUEL CAP symptom test under EVAPORATIVE EMISSION SYSTEM TESTS in SYSTEM & COMPONENT TESTING - GASOLINE article.

5) Check Fuel Tank Pressure Sensor PID Without Pressure Applied

Disconnect EVAP canister outlet tube. Connect scan tool to Data Link Connector (DLC). Turn ignition switch to ON position. Using scan tool, access PCM FTP V PID from PID/DATA MONITOR & RECORD menu. Record FTP V PID value. If FTP V PID is 2.40-2.80 volts, go to next step. If FTP V PID is not as specified, go to TEST HX, step 21) under SYSTEM TESTS.

6) Check for Stuck Open EVAP Canister Purge Valve Condition At Idle

Reconnect EVAP canister outlet tube. Remove plug from EVAP return tube and reconnect tube to intake manifold. Ensure fuel filler cap is properly installed. Turn ignition switch to ON position. Select PCM FTP V and EVAPPDC PIDs from PID/DATA MONITOR & RECORD menu. Start engine and allow to idle. When EVAPPDC PID is zero, FTP V PID should be less than 2.40 volts. If PCM PID values are as specified, replace EVAP canister purge valve. Perform EVAPORATIVE EMISSIONS SYSTEM LEAK TEST . If EVAP system passes leak test, perform EVAPORATIVE EMISSION REPAIR VERIFICATION DRIVE CYCLE . If PCM PID values are not as specified, perform EVAPORATIVE EMISSIONS SYSTEM LEAK TEST . If EVAP system passes leak test, perform EVAPORATIVE EMISSION REPAIR VERIFICATION DRIVE CYCLE .