I am very familiar with that bikes friggin oil light! Very familiar, in deed!

That oil lamp is on the indicator bar just forward of the speedometer. The Oil lamp in the actual speedo is not used.
The RED lamp next to the green neutral light is the low oil pressure light.

It should come on whenever the engine is NOT running and the Key is ON. Should go OUT shortly after the bike starts.

The Handlebar Riser incorporates the wiring and the indicator bar. There is a LOT of wires in that riser! It’s a real fun job to get the cover back on without pinching or cutting wires.

I had one hell of a wrestling contest with a ’03 XL 883 C oil indicator!
First things first though:
See if the Oil lamp on the little light bar is working. If not, unfortunately the first logical step is to check the light bulb. By removing that cover. Protect your gas tank when you play with this! The bars WILL rotate and fall on the tank….
I learned the hard way! If you can find someone to help hold stuff! You better like them though, you are going to be close…. and for a little bit.
It takes 4 hands, 3 arms and no space for another body to hold all this chit together. Oh, make sure the bike is supported very well. It won’t play nice with the front end turned and it will NOT stay straight without help.

If that bulb is good (i check by swapping it with any other bulb that i know works in that line of lights). You will see what i mean when you see how the indicator bar works with the cover off.

Here’s a link to my trials with that oil lamp… This was in 2018, the Thread starts out with oil overflow, but just read on a bit… It gets to that damn oil light soon.