Hi Russ,

Does the 2-1-2 code return after you clear it?
Did you install the O2 sensor, and was it a direct fit or a universal where you
have a chance to miswire it?
If the code returns look carefully at the O2 sensor connector.
Perhaps the harness connector has loose or damaged pins?
Clean with Isopropyl alcohol 90% blow out with air lube with Penetrox-A.
Get rid of the 2-1-2 code.

Connectors and fuse and lamp sockets need periodic TLC.
Shine up and lube your fuel pump fuses and connections with a little conductive grease or even better Penetrox-A.
Do all of your fuse sockets, since corroded 240 fuse sockets are known troublemakers. Don't forget to service the fuses at the battery.

Check that the pins in the fuel relay socket are tight with a 1/4" male spade
lug. You can use Penetrox-A directly into the female fuel relay socket pins
to deter corrosion and improve conductivity.

See if the AMM heated wire is dirty and needs AMM cleaner (no Carb cleaner!), and service it's connector. Use Penetrox-A paste right into the female EFI socket pins.

Make sure there's no air leak between the AMM and throttle body

Bill