Subject : DTC P0446 (Restricted/Blocked EVAP Vent Path) Set, Check Engine Light On (Replace Evaporative Emission (EVAP) vent valve Solenoid Assembly and Add/Relocate Filter Box Using Service Kit).
Models : 1999-2007 Chevrolet Silverado (Classic) Models, 1999-2007 GMC Sierra (Classic) Models, 2007-2009 Chevrolet Silverado Models (Excluding Hybrid), 2007-2009 GMC Sierra Models (Excluding Hybrid).
Condition Some clients whose automobiles are operated in dusty sort environments, similar to farming or mining off street kind functions, might remark concerning the illumination of the check engine light, with a DTC of P0446 (Restricted/Blocked EVAP Vent Path) being set.
Cause Grime and dirt intrusion into the EVAP canister vent hose meeting, leading to restricted air circulation, may cause this condition.
Correction (1999-2007 Classic/Outdated Fashion Fashions) After following the published SI diagnostics for P0446 and figuring out that the EVAP canister vent valve is the cause of the MIL gentle, replace the present EVAP canister vent valve meeting with a brand new assembly. This new meeting is a sealed unit that’s designed to be vented by means of a distant filter box. To ensure correct installation, follow the procedures below.
1999-2003 Model Year (Use Service Kit P/N 19207762)
1. Raise the vehicle. 
2. Disconnect the EVAP canister vent valve electrical connector, if equipped.
3. Disengage the two vent valve pipe clips securing the pipe to the underbody. Remove the clips from the underbody and discard.Disconnect the vent valve pipe at the EVAP canister.
4. Take away and retain the EVAP canister vent valve bracket mounting bolt.
5. Remove the entire EVAP canister vent valve meeting with bracket attached and discard.
6. Important: The new canister vent valve shall be put in in a new location, outdoors of the frame. Position and secure the new valve assembly to the frame bracket on the surface of the body utilizing the existing hole and mounting bolt.
7. Tighten Tighten the bracket mounting bolt to 12 Nm (106 lb in). Join the vent valve pipe to the EVAP canister.
8. Install the two vent valve pipe clips into the present underbody holes.
9. Connect the EVAP canister vent valve electrical connector, if equipped.
10. Connect bulk 5/8″ heater hose to the vent valve port and safe utilizing a clamp. Run a size as needed along the frame rail routing to the area above the transmission.
11. Cut the hose to decided size and install the equipped filter box. Secure utilizing a clamp.
12. Take away the transmission help and lower the transmission assembly as crucial to allow for access to the new filter field location.
13. Safe the filter box to the transmission vent hose just ahead of the hose tee part utilizing a tie strap. DO NOT pinch or restrict the transmission vent hose. The filter box opening needs to be pointing downward.
14. Raise the transmission and reinstall the transmission support.
15. Tie strap the hose as wanted alongside the frame rail in an effort to preserve the hose away from pinch factors and heat sources.
16. Lower the vehicle.