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RD
RD, ASE Certified Technician
Category: Ford
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Experience:  MASTER ASE 35 YEARS
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What do i do to correct the po 446 code on my 2004 f150

Customer Question

what do i do to correct the po 446 code on my 2004 f150
Submitted: 7 years ago.
Category: Ford
Expert:  RD replied 7 years ago.

Hello

Welcome to JA!

 

HX18 DTC P0446 CHECK FOR VISUAL CAUSES OF EXCESSIVE FUEL TANK VACUUM

    • EVAP canister purge outlet tube (EVAP canister purge valve to EVAP canister) blockages or kinks.
    • EVAP canister tube (fuel tank to EVAP canister) blockages or kinks.
    • Fuel vapor elbow on EVAP canister contaminated.
    • Restricted EVAP canister.
    • Canister vent (CV) solenoid stuck closed (partially or fully).
    • Plugged or contaminated CV solenoid filter.
    • EVAP canister purge valve stuck open.
    • Fuel filler cap stuck closed (no vacuum relief).
    • VREF circuit open in fuel tank pressure (FTP) sensor.
    • Damaged FTP sensor.

    Continuous Memory Diagnostic Trouble Code (DTC) P0446 indicates that Self-Test has detected the Evaporative Emission Control System has excessive fuel tank vacuum. Also, a DTC P0446 indicates a vent control malfunction.

    Possible causes:

    Note: If the EVAP canister-CV solenoid and fuel tank assemblies are not accessible to perform the following step, GO to the Powertrain/Engine Group, Evaporative Emissions Section in the Workshop Manual for removal procedures.

  • Check for kinks or bends in the fuel vapor hoses/tubes (EVAP canister purge outlet tube and EVAP canister tube).
  • Visually inspect EVAP canister inlet port, CV solenoid filter and canister vent hose assembly for contamination or debris.
  • Check CV solenoid filter for blockage or contamination.

Is a fault indicated?

Yes No
REMOVE any contamination or debris around fuel vapor hoses/tubes and EVAP canister- CV solenoid assembly. REMOVE kinks or bends in EVAP canister purge outlet tube, EVAP canister tube and canister vent hose assembly. GO to HX19 . GO to HX19 .

HX19 CHECK FOR BLOCKAGE BETWEEN THE EVAPORATIVE TEST PORT AND EVAP CANISTER-CV SOLENOID ASSEMBLY

  • Disconnect and plug the EVAP return tube (EVAP canister purge valve to intake manifold) at the intake manifold vacuum source.
  • Plug (tape) the CV solenoid (or filter) or plug the canister vent hose assembly.
  • Locate evaporative test port [marked EVAPORATIVE SERVICE PORT DO NOT USE UNREGULATED PRESSURE ABOVE 6.89 kPa (1 PSI)] near EVAP canister purge valve or EVAP canister.
  • Install Rotunda Evaporative Emission System Leak Tester 310-F007 (134-00056) or equivalent at the test port.
  • Regulate the nitrogen or argon gas pressure on the tester to 3.48 kPa (14 in-H2O).
  • Pressurize the EVAP system to 3.48 kPa (14 in-H2O).
  • Remove the plug (tape) from the CV solenoid or the plug from the canister vent hose assembly.

Does the EVAP system pressure drop rapidly (quickly)?

Yes No
REMOVE EVAP System Leak Tester from evaporative test port. REINSTALL evaporative test port cap. GO to HX20 . GO to Powertrain/Engine Group, Evaporative Emissions Section in the Workshop Manual for diagnostic symptom condition listed as Hiss When Opening Fuel Cap. REPEAT Pinpoint Test Step HX19 to VERIFY blockage no longer exists. GO to HX22 .

 

 

 

Let me know if i can help more!