Help with 2 codes

[Texas Bulldog]

I was towing my 5th wheel today and had a check engine light come on. P0401 and P101, I looked them up but now what. What fixes the MSF and EGR codes? Is it effecting my power and fuel mileage? It seems to drive and pull fine. any help would be appreciated.
It is a 2006 GMC 6.6 3500 CC lwb 4x4 Allison with a Bullydog 4" and no chips ever.
Thanks,
TB

[Texas Bulldog]

No one here has a clue???????

[Mark Rinker]

PO101 - Mass air flow malfunction
PO401 - EGR Flow Malfunction

Was it raining when the codes were set? Some have reported rain causing the PO101 in the past...

I'd start with searching the forum on both codes, cleaning the MAF sensor (with how-to info from forums), and replacing the OEM air filter if its due. (Am assuming you are running stock filter, if aftermarket be aware of over-oiling...)

If you clear the codes, do they (both) return? I am thinking the two are unrelated.

[BobbyV]

Texas Bulldog,
The EGR code P0401 was likely the result of the mass air flow malfunction P0101, as the EGR diagnostic uses the MAF signal to confirm EGR flow. Your truck uses a dual sensor, mass air flow and intake air temp. Remove the intake air duct and check for restrictions on the MAF sensor inlet screen. Also look for possible air leaks downstream of the sensor. Check the integrity of the sensor's o-ring seal.

PS: I'm married to a Texas A&M grad. God Bless Texas!