05 Denali wiring issue

[Rwg815]

I have an 05 denali xl with 154000 miles. I have been having an issue for a few months now. When it's parked and idling it's starts to shake and turn off. When I'm driving it starts to jump and feel like it's going to die. It's not setting any engine codes. My mechanic is convinced it is the engine Wire harness but before I spend 800 on a new harness was wondering if this is common and if anyone has had this happen to them.

 

[MrBalll]

Sounds like a fuel pump to me.

 

[Rwg815]

Sounds like a fuel pump to me.

Would the fuel pump set a code

 

[Cattivo]

Yes it will, P0171

 

[Rwg815]

Yes it will, P0171

im not getting any codes and the previous owner said he changed the fuel pump