I have a 2003 Yukon with a 6.0 LQ4 I bought it cheap with 125k. the previous owner thought it needed a motor , which it might. The oil pressure gauge shows 0-20 lbs pressure most of the time and ding ding goes all the time. The last owner put in a new pump. I hear some ticking when it is warm. I started it very cold today, had 25psi and no ding ding, no ticking, ran almost perfect. it ran rough for the first 30 seconds then smoothed out and ran smooth and quiet. I didn't let it warm up all the way. The other day it was very low and it just popped up, then when back down, all at the same rpm. It seems as though the OEM pump is not very good and a new one can't be relied on, can this be a sketchy pump?

 

I don't think it's the pump. You might just drop the pan, and slip a new set of Rod and Main Bearings in it. The other major culprit for low pressure is Cam Bearings.

 

I am afraid of just that. I got a new salvage yard motor with 68k for cheap enough that it makes more sense to just chuck the old one. I am very comforted knowing there is such low demand for this motor that it is so cheap.