just put a new "used" engine into a 07 sierra (new style gen 4), and the oil pressure was a little low, but still in spec. The issue was that the gauge was stopping at 40lbs under high rpm. I installed a mechanical oil pressure gauge on the lower front drivers side port of the block and drove around to see how the pressure was.

Even though the low pressure at hot idle was still the same ~25psi, the mechanical gauge would top out at 70psi, where the electric would stop at about 40psi.

I put a brand new oil pressure gauge when I installed the engine, and all the wiring was good with no issues.

Just wondering how I go about getting the electric sender/gauge reading properly

 

You would need a factory scan tool to test it. There is an option to sweep the gauge cluster. Most likely the stepper motor is bad in the cluster.

You would also need to see if the sender is reading the same as what is being displayed on the cluster.

 

well I put on my scanner and the sweep test was fine,

I checked the sensor and it was only showing 16kpa with the engine off where it should be 100kpa(atmosphere)

With the engine running it was also showing about 140kpa at idle which doesnt really make sense since 140kpa is around 6psi and the dash gauge was showing ~20-25psi which is ~250kpa.

I dont understand how the sending unit is sending 140kpa, but the dash gauge is showing around 250kpa.

The other issue is that the dash gauge doesnt get past 40psi and it is very delayed as well.

I have a brand new sensor installed, and I inspected the connector and wiring. I checked the schematics and all 3 wires go into the engine computer so I am stumped.

any thoughts?

 

just went through and tried a different oil pressure sender, no difference

just checked resistance on all 3 wires at the plug to the engine computer plug and they were good

basically its showing 16kpa at atmosphere when it should be 100kpa. I can't figure it out!

 

Where are you getting the senders from???