i am coming up with codes P1590 and P1171.

my main mechanic which has worked on my discovery for the last 4yrs says he cant figure it out. He says its running rich but doesnt know why. I looked up on previous posts that p1171 o2 sensor system too lean. but i cant find what P1590 is? is it related? any insight please, i cant drive my truck until I get it fixed....... thanks again

 

If it is running rich it has to be bad O2 sensors, in need of a tune up, a vacuum leak or maybe a bad MAF sensor.
I am assuming that you guys checked the normal stuff like the air filter.