'06 Denali 1500 experiencing Fluctuating & Low Oil Pressure

[CigarXO]

Last month my '06 Denali 1500 developed an oil pressure reading which pegged out at Max even when the truck was off, but electrical accessories engaged. So, I - with the help of my daughter with tiny arms/hands - completed the PITA job of accessing and replacing the Oil Pressure Sensor. It appeared to fix the issue with normal readings for the month, then this week I now have low and fluctuating readings, with warning bells and ECU readings. I can't determine one scenario which causes the reading to fluctuate: under load, hill, idle. There is no engine noise or temp issues to make me think it is a mechanical issue.

2006 GMC Sierra Denali Crew Cab 143.5" WB AWD VIN: 2GTEK63NX61240681

LQ9 Vortec 6000 V8 SFI   GEN3 motor = it doen't have the filter screen under the OP sensor.

 

Here's my diagnosis to date:

 

I grabbed a HarborFreight oil pressure gauge: https://www.harborfreight.com/Engine-Oi ... 62621.html for $24.99
and a Gen3 J-42907 like adapter from Amazon: OTC Tools 7219 Oil Pressure Adapter for $53.98

Warmed the truck. Checked the oil levels one more time (fine). Removed the oil filter and put on adapter & gauge. Ran the truck. At first the gauge read steady 40ish - I thought - yeah, the oil filter was bad.  The truck's Oil Pressure gauge resumed the same behavior, except now it is more likely to drop to zero reading and remain whereas before it fluctuated 5-40. The manual gauge showed normal readings ~40psi with increases with RPM. Here is a recording of the test:
https://www.youtube.com/watch?v=P5COmRAdKxU

I'm going to go pull off the manifold covers and get to the sensor again to check the wiring connection. Otherwise... what's next?

Thanks in advance!
CigarXO

[Trevor Johnson]

I would use a new gm sensor, I would also clean the electrical connection to the sensor. I have seen them leak through the sensor and cause strange issues.