My mom's 98 explorer is throwing the code P1131 which means that it is lean on bank 1. First, what the heck does that mean? I have done some more research on line and cant find a good answer. And two, how could I fix it? I have seen multiple things fix this and I do not know where to start. Thanks guys.

 

Anyone with a 4.0L ever get this code? I am gonna check the o2 sensors tomorrow.