I helped swap a blown 305 HP engine with a newer 3rd gen engine in a 2003 Dodge truck.

We swapped over the entire engine wiring harness including all sensors and the ECM itself.

Everything works great but the oil pressure gage reads low. We checked the oil pressure with a mechanical gage and its 25PSI at idle, 70 PSI going down the road. However the gage in the truck shows just above the red at idle and 3/4s going down the road. The problem with this is that we get feeling that the engine doesn't have good oil pressure at idle even though it does.

We've swapped in several new sending units with no change in how gage behaves.

Why doesn't the gage show higher oil pressure at idle ?

 

Could it be the guage and sender are not matched? Are you using a sender for an 03 truck?

 

newer 3rd gen engines don't have a oil press sender, only a 6psi switch(open-closed) the pcm has a pre-programed oil pressure senario that it sends to the oil press guage. acutal oil press and guage press are not related,the guage reading is just an imaginary reading of what the engineers think you should be seeing

 

Raycarlson is absolutely correct. Our oil pressure guages are glorified idiot lights. The only time the guage is 100% accurate is when it reads zero. As long as the sending unit senses pressure, the guage reacts to a "program" that is designed to make you feel better.

Same thing on a Ford.

Sad but true.