Vehicle is a 2005 6.0 power stroke diesel.

Hello. I am dealing with this P0402 that I cannot seem to get rid of.

Initially I had a code of P0405 for dead egr valve. No other codes were present at the time. I went and picked up a new egr valve not ford but another brand from oreilly with lifetime warranty and installed it. The old egr valve did not have any soot or wetness thankfully .

Everything was okay for about 30 min or so. While driving around the P0402 code popped for excessive egr gas.

After doing research it looks as if the MAF is used to measure egr and could possibly be dirty. I pulled the maf and cleaned it and put it back in and cleared the code.

About a week goes by and the light pops back up for P0402 again.

There was an after market filter on the vehicle and I noticed a tear in the filter media. Figured I replace it, so I went with a k&n. Again I pulled the maf, cleaned it and also installed the new filter. I’ve read that people have seen the P0402 code pop when having aftermarket filters as they don’t filter out as well as the stock one.

Another week goes by and the darn P0402 light goes. So now I am stuck trying to figure out what to check.

Truck has a monitor but is on stock tune. Deltas between eot and ect on the freeway at 75mph is 2-3 degrees.

Can anyone recommend what else to look at? I’m looking at either replacing the k&n filter and going with stock or maybe replacing the maf.