Download 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) This bulletin is being revised to provide an updated picture of the remote filter box and to add an important statement to not replace the EVAP canister. Please discard Corporate Bulletin Number 02-06-04-037E (Section 06 — Engine/Propulsion System). Condition Some customers whose vehicles are operated in dusty type environments, such as farming or mining off*road type applications, may comment about the illumination of the check engine light, with a DTC of P0446 (Restricted/Blocked EVAP Vent Path) being set. Cause Dirt and dust intrusion into the EVAP canister vent hose assembly, resulting in restricted air flow, may cause this condition. Correction (1999-2007 Classic/Old Style Models) After following the published SI diagnostics for P0446 and determining that the EVAP canister vent valve is the cause of the MIL light, replace the existing EVAP canister vent valve assembly with a new assembly. This new assembly is a sealed unit that is designed to be vented through a remote filter box. To ensure correct installation, follow the procedures below. Important: DO NOT replace the EVAP canister assembly for this concern unless it fails the leak test. 1999-2003 Model Year (Use Service Kit P/N 19207762) Raise the vehicle. Suitably support the vehicle. • Disconnect the EVAP canister vent valve electrical connector, if equipped. • Disengage the two vent valve pipe clips securing the pipe to the underbody. Remove the clips from the underbody and discard. • Remove and retain the EVAP canister vent valve bracket mounting bolt. • Remove the complete EVAP canister vent valve assembly with bracket attached and discard. • Important: The new canister vent valve will be installed in a new location, outside of the frame. Position and secure the new valve assembly to the frame bracket on the outside of the frame using the existing hole and mounting bolt.