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P0446/P0451 code

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So a couple of weeks ago my check engine light came on my way home from work. I ran my scanner and got P0446 and P0451. Now whenever I try to get gas the tank wont allow me to fill up. My gas cap makes a hissing sound and air tends to suck the cap back. I can use a gas can just fine but sometimes ill hear a gurgling sound as if air is getting trapped. Have a family friend who's a mechanic and he said hes never dealt with this problem before. He took the evap canister off and cleaned it and the problem is still here. 2013 Silverado 5.3l. suck having to fill up my truck using a gas can every day. was wondering if somebody else has had this problem before and fixed it before I bite the bullet and take it to a dealership to get it fixed.

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Failing gas tank evap vent solenoid is a problem on some of this generation.


It sits right on top of the fuel pump module. It’s a fairly cheep GM part too 👍🏾

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15-06-04-002: Malfunction Indicator Lamp (MIL) Illuminated, Fuel Tank Hard to Fill, DTCs P0442, P0446, P0455 or P0449 Set



Some customers may comment on the following conditions:

  • The malfunction indicator lamp (MIL) is illuminated.
  • The fuel tank is hard to fill.

Technicians may find one or more of the following DTCs: P0442, P0446, P0455 or P0449 set as current or in history and there may be evidence of dust or water intrusion at the evaporative emissions (EVAP) canister vent solenoid (CVS) valve.


The EVAP CVS valve draws fresh air into the EVAP system through a vent attached at the top of the conduit that is secured to the fuel filler pipe. Under certain operating conditions, dirt and dust intrusion into the CVS fresh air intake/venting system may result in restricted air flow.

Under certain operating conditions, if water is ingested into the EVAP CVS fresh air intake/venting system, it may reach the CVS valve causing corrosion in the CVS valve and may cause restrictions in the fresh air intake path when the CVS valve is in the closed position.

Ingested water will also collect in the CVS valve cyclonic filter in order to protect the EVAP canister. However if the capacity of the cyclonic filter is exceeded, this may result in water entering the EVAP canister and cause an additional restriction during refueling.


Note: DO NOT replace the EVAP canister assembly for this concern unless it fails the leak test or it has ingested excessive amounts of dirt, dust or water.

After following the published SI diagnostics and determining that the EVAP CVS valve is the cause of the Malfunction Indicator Lamp (MIL) illumination or the hard to fill symptom, replace the existing EVAP CVS valve assembly with the new revised design assembly.

Object ID: 4139214Click here for detailed picture of the image.

Original design EVAP CVS valve shown above.

Object ID: 4139674Click here for detailed picture of the image.

Revised design EVAP CVS valve shown above.

This revised EVAP CVS valve assembly is a sealed unit that is vented through a remote pre-filter mounted atop the fuel filler housing. The revised CVS valve incorporates improved filtering capacity. To ensure correct installation, follow the procedure outlined below:


Important: DO NOT make any sharp bends or allow any kinks in the hose when routing the hose.


Note: Apply loc-tite 401 or equivalent (SuperGlue, etc.) to the end of the heater hose (1) which will go into the CVS valve rubber coupling.

  1. Turn OFF the ignition, and all electrical components, including the scan tool.

    Note: DO NOT remove the fuel fill cap in order to prevent any debris from entering the fill pipe.

  2. Remove the fuel tank filler pipe housing to body TORX screws and retainer.
  3. Reposition the filler housing and pipe to improve access to the EVAP pre-filter located on the top of the fuel filler housing.
  4. Release the tabs (1) securing the EVAP pre-filter housing (2) to the top of the fuel filler housing.
  5. Raise and support the vehicle. Refer to Lifting and Jacking the Vehicle in SI.
  6. Disconnect the vehicle chassis wiring harness electrical connector from the CVS valve.
  7. Disconnect the CVS valve assembly quick connect fitting from the EVAP canister. Refer to Plastic Collar Quick Connect Fitting Service in SI.
  8. Note the routing of the pre-filter hose along the frame rail and fuel fill pipe assembly, then disconnect the filter line clips and remove the filter assembly/line from above the frame rail and fuel filler pipe assembly.
  9. Cut off the CVS valve assembly line with quick connect fitting from the CVS valve as shown above.
  10. Remove the complete CVS valve and filter assembly/line from the CVS bracket on the vehicle.
  11. Install the cut off the CVS valve assembly line with quick connect fitting to the CVS valve as shown above. Match the approximate angle of the line on the original valve and clamp into place.
  12. Install the new CVS valve assembly to the vehicle.
  13. Measure the length of the hose on the removed EVAP CVS assembly from the pre-filter to the CVS filter. Allow extra length to ensure there will be no kinks in the heater hose, and cut the needed length of the specified heater hose. The hose will run along the frame rail in the same manner as the original pre-filter hose.
  14. Install the new pre-filter and filter housing to one end of the hose and clamp in place.
  15. Partially lower vehicle.
  16. Through the fuel tank filler pipe housing opening, install the pre-filter and housing (2) with hose attached to the back of the fuel tank filler pipe housing. Secure the tabs of the filter (1) to the slots in the filler pipe housing.
  17. Install the fuel tank filler pipe housing to the body.
  18. Raise the vehicle.
  19. Carefully route the pre-filter hose along the fuel filler pipe and frame rail and over to the CVS valve assembly.
  20. Install tie straps along the pre-filter hose to the fuel filler pipe and wiring harness along the frame rail.
  21. Trim an excess hose length as needed.
  22. Apply adhesive as indicated and install the hose into the rubber coupling of the CVS valve assembly. Ensure the hose is fully installed and clamp into place.
  23. Connect the vehicle chassis wiring harness electrical connector to the CVS valve.
  24. Lower the vehicle.
  25. Clear any DTCs.
Parts Information

Part Number








HOSE, FUEL-OIL EVAP 5/8" x 25' (need 3-8 feet from roll per vehicle depending on box and CVS configuration)

Cut Length


TIE STRAP (need 4-6 depending on box and CVS configuration)




Object ID: 4139874Object ID: 4140029Object ID: 4140080Object ID: 4140104Object ID: 4140133Object ID: 4139874Object ID: 4140315Object ID: 4140318Object ID: 4140350Object ID: 4140476
Object ID: 4140575Object ID: 4140673

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