LT1, LT4, L83, L86, LV1, LV3 Air Filter Seal Leak can cause issues

[Bruce Nunnally]

Air Filter Box Seal Leak

On some 2014-2016 Corvette, Silverado, Sierra; 2015-2016 Escalade models, Yukon models; and 2016 CTS and Camaro equipped with a V8 engine (RPOs LT1, LT4, L83, L86, LV1, LV3), the MIL may be illuminated and DTCs P0420 (Catalyst System Low Efficiency) and P0430 (Catalyst System Low Efficiency Bank 2) may be set. These conditions may be caused by excessive dirt/debris entering the air filter box and bypassing the seal of the air filter, causing damage to the H02 sensor element (Fig. 15) and blocking the catalytic converter. (Fig. 16)

Fig. 15

Fig. 16

Do not replace any parts for these conditions until the air filter housing has been validated to be completely sealed.

Inspect the air housing cover for any missing tabs or fasteners. Also remove the air filter housing cover and inspect the seal around the filter as well as the air filter sealing surface for signs of not contacting the air filter seal. (Fig. 17)

Fig. 17

In addition, look for dirt/debris in the air filter housing cover bypassing the air filter. (Fig. 18)

If dirt/debris is bypassing the air filter due to a faulty seal, replace the air filter. If the air filter housing is not properly sealing, refer to the appropriate Service Information for additional diagnostic procedures.

Fig. 18

ref: http://sandyblogs.com/techlink/?p=5924

[Cadillac Jim]

Sealing an air cleaner box with a new element can be quite difficult. Not once did I find the air cleaner box in my Eldorado properly sealed, and I found it impossible to close and seal properly in-place. I removed the whole assembly and sat on it on the garage floor to get it to close and apply all the clamps properly, then put it back into the car.

The stiffness of the air cleaner box may or may not have been because of its age by the time I started to DIY for these things but if the newer cars are anything like it, I suspect that all of them will have the same problem to some extent.

Bruce, you got me. I'm going to check my CTS-V air cleaner ASAP. The TSB may cover later models but...

[Bruce Nunnally]

I am not clear on why this problem occurs. The air filter has a specific gasket or sealing area, the housing has a specific seating area for the air filter gasket area. So either the filter is not stiff enough, or the box is not stiff enough, or the box doesn't actually compress the air filter gasket area?

OR maybe the supercharged engines need more sealing? But this covers both normally aspirated & supercharged.

[barczy01]

If the air box was leaking wouldn't it cause a lean condition? Also, your telling me debris is getting past the air filter, intake manifold, combustion chamber and somehow finding an oxygen sensor? Maybe adding a secondary filter on the air filter for fine particles?

[Bruce Nunnally]

The airbox is upstream of the MAF so the air measured is correct. The tech article asserts that the issue is debris gettng through the maf screen and combustion process to the o2 sensors in frnt and behind the cat. Curious.