2003 Chevy Tahoe Oil Sensor & Fuel gague

Welcome to the forum. How many gas tanks? What is the size of gas tank? Any codes? There could be some fuel level sensor codes?

Sometimes, I take the connector loose from the gas tank, use a resistor on the proper terminals for the fuel level sending unit. Turn key on, see if gage reacts differently to different size resistors. Some of the info I looked at shows the higher resistance, the higher voltage signal, sounds backward to me? empty-- 66 ohms, 1/2 tank-- 140 ohms, full tank 250 ohms. The voltage signal runs from 1 volt--2.5 volts depending on the fuel level. The info I looked at was for 26 gal tank, the specs are approximate. If the gage reacts properly, then everything from the connector forward should be ok and the problem is probably the sending unit in the tank. You need to test when the problem is ongoing and intermittent problems can be hard to track.

The truck has one fuel tank approx 20 gallons. I'm unsure regarding to the codes, is this something I can dertermine without taking it to a shop? It seems both the fuel and oil gauges operate incorrectly at the same time. Yesterday both gauges where fully to the right..some times they work fine. Do you feel this problem could be related to both?

Might be a problem with instrument cluster? Some of the national brand autostores will check some codes for free, don't know about manufacturer specific codes?