Water Intrusion into the Air Filter Assembly

If water or snow gets into the air filter assembly on some 2017-2018 Silverado and Sierra models equipped with the 6.6L Duramax diesel engine (RPO L5P), it may saturate the air filter and reduce flow to the point that the filter is damaged. Under this condition, the Check Engine lamp may illuminate and DTC P0106 (Manifold Absolute Pressure (MAP) Sensor Performance) also may set.


The water or snow intrusion may be due to the air induction filter box being out of position or other vehicle modifications, which may alter the seal between the hood and inner fender.


The induction system on the 6.6L Duramax diesel engine is designed to prevent water and snow from entering through the hood duct. If the seal is compromised, water or snow can reach the air cleaner element along with warm air pulled from under the hood. In colder temperatures, moisture in the air filter assembly may freeze and block the air filter with ice.


In addition, if the vehicle is operated in temperatures below 0° F (–17° C) and a front-end grille cover is not used, snow can be pulled through the grill duct and, over a period of time, the filter may accumulate enough ice to reduce airflow.


Air Filter Box Position


Confirm that the air filter box is in position, secured to the air filter box bracket (Fig. 12, #1), and that it is sealed to the inner fender (Fig. 12, #2) and the hood gasket. (Fig. 12, #3)


Fig 12


Check the Seal


Check for a proper seal between the air filter box upper gasket and the hood by wetting the gasket (foaming glass cleaner can be used) and closing the hood. Open the hood and look for a contact ring witness mark around the entire hood duct opening to the air cleaner assembly. The following photo shows a leak (no contact) at the front edge of the seal. (Fig. 13)


Fig. 13


Vehicle Modifications


Any vehicle modifications to the front grille, hood or fender also can affect the seal between the hood and inner fender. The Original Equipment Manufacturer (OEM) bumper on the Silverado and Sierra have intake air filter assembly protection (Fig. 14, top) to help prevent moisture and debris from entering the assembly. Aftermarket bumpers may not be equipped with the same features to properly protect the air filter assembly. (Fig. 14, bottom)


Fig. 14


– Thanks to John Stempnik


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