Low Oil Pressure Help 2005 Silverado 1500

[chevydude2015]

I've been getting a low oil pressure warning that sets off the chime in my 2005 Silverado 5.3. My mechanic has verified that the oil pressure is norma and has replaced the oil pressure sending unit.

 

This has not fixed the issue which leads us to believe that either 1. the connection for the sending unit is bad causing a false reading or 2. the actual gauge on the gauge cluster is bad. 

 

Before I tear into the gauge cluster, does anyone know what triggers the low oil pressure warning/chime? Is it the sending unit itself or the gauge on the gauge cluster? This will help tell me if the gauge cluster is bad or if the connection for the sending unit is bad. 

 

Thanks in advance. 

[chevydude2015]

Also to add, the oil pressure gauge normally will read ok at startup and then begins to fluctuate but after 5-10 mins of driving it will go to 0 and then will bounce upon occasionally just enough to set off the very annoying low oil pressure warning and chime. Eventually, it will stay at 0 and the low oil pressure warning will stay off unless I hit a bump in the road. 

[dna9656]

Are you aware of the Oil Pick up Tube to oil pump O ring issue? The O ring leaks....I don't know what years are involved but there is a TSB on it. I replaced my pick up tube, the O ring (of course) added an additional keeper for the pick up tube (avail on Amazon; if you want more info PM me)the Timing chain and sprockets along with a new Melling High VOLUME oil pump. I now have 40 PIS pressure at ALL times. I had a 06 Avalanche 5.3l.