Fuel pump not coming on

I always find it difficult to get the total picture across when trying to ask a question so I apologize in advance. I have a 2003 yukon. I had the fuel pump replaced about 1 year ago. About 2 weeks ago the check engine light came on. The other day when I started it the fuel pump sounded weird. Then it started and it idled really low. When I pushed the gas it was almost like I wasn't. Seemed pretty gutless. It has been sluggish since. I filed up the other day and it seemed to run better, got to a half tank and running icky again. Today I tried to start it and out was on a slight hill.it wouldn't start. The fuel pump wasn't making a noise at all. So I pushed it to flat ground and it started. The fuel pump was making a knarly sound though.
The code coming up from the check engine light is P 042. Thanks so much for listening to all that! Any ideas what it could be? Fuel pump? Fuel sensor? Fuel injection?