My 2004 H2 oil pressure guage was sitting on the red line...at zero basically. Pulled it over...checked oil...great..no knocking noises (sounds brand new still) and no overheating no check engine light...nothing...except zero oil pressure...drove it the three miles home...no issue...if this was sk mething more than a bad guage it would be obvious I'm hoping? Any help appreciated. 04 completely stock garage kept.

 

Most likely the oil pressure sending unit. Not a costly replacement, just a complete pain to get to since it's on the back of the engine next to the firewall. Good luck!

 

Sending unit or the gauge I would go for the sending unit first.

 

https://www.hummerforums.com/forum/h...eplaced-35938/
Check If you need to replace the oil sending unit
Replaced a few weeks ago . For sure will consume your patience. . Even remove the plug took me 30 min .. still the job isn't complicate
Make sure you have a camera (cell) to look bavk there and removing the fuel lines make it 90%easier