Oops! 87 octane in my ‘03 3.4L s/c triggered CEL

Okay. Clearly I’m no mechanic, so please share any advice, info, critiques,& past experiences. I’m really here to learn, but unfortunately this time it’s the hard way.

 

The o2 sensor referenced in that code is failing. Actually, the heating element in the sensor. If the code doesn't come back right away you may be ok for a while. Otherwise the sensor needs replacing. Replace it with a Denso brand sensor.

There is a lot of info on TW about this. Worth reviewing. It is a fairly common occurrence on these trucks.

 

Went and bought a code reader. After erasing the code it comes back on within 15-30 second after starting. The warning prompts me that I should get it fixed asap. So I went and bought the new denso senor which I am going to replace. However it says it may damage other components if I don’t fix it in the warning. Does this refer to my internal engine components? Or what would get damaged if it’s not replaced

 

Update!! I finally got around to replacing the upstream O2 sensor and the CEL is now off and staying off. Success! Always nice when things are simple. For those who are looking to do the same. If u don’t have fancy tools all I had was a flathead screwdrive to undo the electrical connector from the frame, and a 1/4” ratchet with a shallow 12mm socket. Things turned right out with no penetrating oil or heat which blew me away cuz they were rusty af