3.5L EB with max tow package less than 5k miles. Installed k&n filter kit, and check engine light came on when coming back with our 5,000lb travel trailer. Dealer claimed it was the PCV sensor that needed to be replaced but also said the K&N could be the problem. Drove for about 300 miles before attaching the trailer and throwing another light on the trip home again. Dealer replaced a PCV tube this time but is pointing fingers at the K&N. I can't help but to thing this is a towing related issue (or defect with the truck) and not K&N. Anyone have any thoughts on why a truck with less than 5k is throwing lights when towing? Someone also mentioned needing a trans tune with the K&N, but I find that hard to believe.

 

Does the problem disappear when you reinstall the original (or equivalent) filter? What code is being thrown exactly? You mass airflow sensor could also be dirty, try cleaning it.

 

The problem has not come back after removing the K&N, but the only towing trip was short and flat. I can't say this is conclusive yet. I have another trip to the mountain/hilly area in three weeks which will be the true test. If I make it back from that trip with no light, I'd say it was the K&N, but we have to wait and see.

The codes being thrown were P04DB and the dealer replaced the PCV valve the second time the light came on. First time, they replaced the PCV sensor.

 

Is is just a K&N filter or is is the whole K&N intake? If it's the latter, the excess airflow is probably what's causing the issue then.

 

The whole intake. I would think the more air, the better, no?

 

No.

 

I don't know enough to answer that question. I only know enough to tell you about the problem you're having. The sensor in your vehicle is reading the excess air as a leak into the crankcase which is, in all likelihood, caused by the higher flow intake. You would either have to restrict the flow to be equivalent to stock or replace the K&N with the original intake.