1990 Honda Accord code 41

Check engine light comes on.
I checked the service connector and received 4 long blinks followed by 1 short. I made sure to check it multiple times with the same result. Code 41
I replaced the heated sensor yet I'm still receiving the code 41. There's no stutter, no stall. The car seems to run fine. Any ideas why I might still have my check engine light? I removed the backup fuse as well as the negative terminal, but nothing changed.