C15 6nz low oil pressure fault code

I would inspect the oil psi sensor at the body, they will usually start to leak and the sensor body comes loose. It may be failing electrically and glitching faster than it can report to the gauge, but the ecm picks it it up.

 

Is there one or two oil pressure sensors on your 6NZ? May be you have one for your gauge and another for ECM input...

 

I have a 6NZ Cat in a 2003 pete 379x. I also have had that a few times, but CAT said they cleared the code and to advise them if it happens again, which it did. They next uploaded the latest updates (newer version) into my ECM and it never happened again.

 

My oil pressure gauge gets stuck about at 5psi, it will read like at 60 psi when normal is about 65. I just tap on the gauge and it goes back to normal. I would get a Cat ET and see what it reads. Or just go the less expensive route and replace the gauge and sensors as said above.