So I have an 03, and she's currently starting but immediately stalls out. I am pretty new to the mechanic world with very little knowledge. Anyways, when I insert the key, only the indicating lights will turn on, no chime however, and no speedometer/tachometer lights turn on (the theft light seems to be normal btw). But I noticed that with the OBD2 scanner plugged in, everything besides the chime noise comes on and she'll start and continue running like normal. I suspected a ground somewhere, but I do not know where to start.. I also had replaced my ignition switch and nothing changed lol

 

Check the two starter relays one is in the side fuse box the other is under the hood had a similar issue.

 

Have you at least fiddled with your truck?
Be more descriptive AND COMPLETE with posts.

Here's what you posted, with the fluff removed.
1) an 03 WHAT ENGINE, TRANS, ETC.?
2) currently starting but immediately stalls out...POSSIBLY AN INCORRECT KEY
3) when I insert the key, only the indicating lights will turn on...You mean the common dash lights?
4) no chime however,...?? weak battery?
4) and no speedometer/tachometer lights turn on///You mean the background lights?
6) the theft light seems to be normal btw...You mean it isn't flashing?
7) But I noticed that with the OBD2 scanner plugged in, everything besides the chime noise comes on and she'll start and continue running like normal. Have you driven it in that configuration?

MY PROGNOSIS:
There are grounding straps which are made of woven copper wire. They oxidize... turn to dust.
Replacing them is likely overdue. Engine to firewall Box to frame
Inspect all your big cable connections for corrosion and tightness.