error codes (2)

[MrCobra]

My sons Check engine light has been on in his 2001 GMC Jimmy so he had it checked by a friend. Came back with 2 codes. P0101 & P0410

P0101-Mass Airflow circuit range performance problem
P0410-Secondary Air injection system melfunction

I am assuming the P0101 is the mass air flow sensor needs replaced ?

Also would the P0410 have anything to do with the 4wd being out? He says he only has rear wheel drive now or that has nothing at all to do with the P0410

And the P0410 I have absolutely no clue as to what that is so any help would be greatly appreciated.

thank you

[old_master]

Always repair the first DTC in the order they were retrieved, first. In your case, if the P0101 was first, diagnose and repair it before going on to any other DTC's. The DTC indicates a problem exists, it does not say replace the MAF sensor. P0101 can be set for any number of reasons, not only a faulty MAF sensor. Inexpensive, quick and easy tests are: Check for 5VDC reference voltage at MAF connector. Check for less than 5 ohms resistance to ground at the MAF connector. Check for air leaks in the tube from the MAF to the throttle body. Check fuel pressure and leakdown rate.