Chevy P0455: GM’s Large EVAP Leak Checks (2000–2021 Gas)

GM released 21-NA-124 in May 2021 as an information bulletin: diagnostic tips for a lit MIL with P0442 and/or P0455 stored in the engine control module. It covers Buick, Cadillac, Chevrolet and GMC passenger cars and trucks, medium duty included, from 2000 to 2021, and it applies only to vehicles with gasoline engines.

The same bulletin covers P0442, the small-leak code. The two codes share GM’s connection list and inspection order but not every cause. A purge valve stuck closed appears only under P0455.

The bulletin helps locate the leak; it is not a parts procedure. It reminds technicians to follow the service information document for the vehicle and code in front of them.

GM lays out four steps and asks that they be taken in chronological order. The sequence mirrors the bulletin’s list of P0455 sources: connections and lines come before either valve.

Two testing notes apply along the way. GM recommends checking both ways, under pressure and under vacuum, because some leaks are noticeable under one condition only. Cycling the purge and vent solenoids with GDS2 while inspecting may point to a sticking valve. Both are shop procedures.

GM’s order of checks in 21-NA-124, PDF pp. 1–2.

21-NA-124 names seven critical connections that could likely lead to P0442 or P0455. In GM’s order: the purge tube to the purge valve, at the intake manifold; the purge tube to the chassis EVAP line, at the rear of the engine near the transmission; the chassis EVAP line to the canister; the fuel tank load line to the canister; the vent valve line to the vent valve; the fuel tank load line jumper connection, near the fuel tank; and the fuel tank cap, closed properly, at the refuel compartment.

GM considers it likely that one of these joints is not properly seated or that its line is damaged. The last item, a fuel tank cap closed properly, is one an owner can check. The other six are part of the technician’s inspection.

23-NA-073, a June 2023 technical bulletin, lists P0455 with P0442, P0446 and P0449 on Silverado and Sierra trucks run in extremely dusty environments. GM gives the cause as the normal use of these vehicles in severe dust, which can enter the EVAP system and plug the canister and canister vent solenoid.

The correction adds a filter between the canister and its air inlet. It is a customer-pay alteration, and all repair and payment authorization has to come from the owner. GM calls the filter a maintenance item that should be checked periodically so the condition does not return and the code does not set again. For a retrofitted truck that comes back with the same condition, the repair can be the filter itself.

Model years differ between the 1500 and the heavy-duty trucks; the application list on this page gives each series.

09-06-04-028D, revised in April 2014, covers the 2007–2010 Cadillac Escalade models, Chevrolet Avalanche, Suburban 1500 and Tahoe, and GMC Yukon and Yukon XL 1500 models.

GM explains the air path. The canister vent solenoid (CVS) valve draws fresh air through a vent at the top of a conduit secured to the fuel filler pipe. Dirt and dust in that intake can restrict airflow. Water that reaches the valve can corrode it and restrict the fresh-air path when the valve is closed. A cyclonic filter at the valve collects ingested water to protect the canister; once its capacity is exceeded, water can enter the canister and add a restriction during refueling.

Revision D added correction details for the 2008–2009 hybrid models, updated the labor operation to Global Labor Code 4080448, and replaces 09-06-04-028C.

Only 09-06-04-028D lists a labor operation, for vehicles repaired under GM’s Emission coverage. GM points technicians to the Applicable Warranties section of Investigate Vehicle History (IVH) for coverage information, and marks the operation as unique to the bulletin, not published in its Labor Time Guide. The figure is hours, not a price.

21-NA-124 requires no parts and lists no labor operation. 23-NA-073 lists none either: GM classes the dust filter retrofit as a customer-pay alteration, not a warranty repair.

GM warranty labor time for the 2007–2010 models in 09-06-04-028D, PDF p. 7. Hours, not dollars.

All three documents end with GM’s standard notice. They are written for trained technicians who have the equipment, tools and safety instructions for the job, not for do-it-yourself repair, and a listed condition does not mean a particular vehicle has it. The notice sends owners to a GM dealer to learn whether a bulletin may benefit their vehicle. When booking, bring the stored code and say whether the tank has been hard to fill.