Replace the drivers side, downstream O2 sensor today after getting the P0141 error code on my 2000 Suburban (5.3). Disconnected the battery for a few minutes, started the truck, and the SES light is still on. Felt the sensor with the truck running and it was barely warm.

One thing about the sensor - it's an AC Delco that I got on clearance at Rock Auto. Physically it looked like the right replacement (same threads, same hex size) but the electrical connector had 2 plastic tabs inside of it (to make sure it connects the right way) whereas the old connector only had one. Because of the extra tab it did not fit. I ended up popping out the pins and swapping the connectors.

Anyone ever experience this with their new O2 sensor? What should I look at next?