p0138, replaced o2 sensor and lights still on

im a bit confused, it was showing a code (i 4get the number) and i replaced the o2 sensor, the one after the cat, after doing it the lights still on, so i scanned it, and it comes up p0138, from what i understand that also means the second sensor, the guy at autozone said it take about 50 miles of driving for it to check into the system and go away, i never heard of such a thing

after researching i see that some people dissconnect there battery when doing it, should i dissconnect it for awhile?

yes, i usually reset the code after repairs (by disconnecting the battery), but you can also just drive it and it will go away if the problem is fixed but it usually takes around 500 miles and 10 (up to temp) key cycles.

i just dissconnected the neg battery cable, whenever i decide to go out today i'll hook it back up and see if the lights still on