Check engine light on - Need O2 sensor??

[ACir]

Light came on this morning right after start, and was still on when I got to work. Got a fault code of 1221 from the OBD. Should I change the O2 sensor? If I change it, should the check engine light go off by itself if that was the fault? Thanks in advance for anyhelpful feedback.

[Erick]

Which car do you have? I replaced my O2 sensor (91 535i) after a CE light and 1221 fault code. No effect - I still get the CE light, the 1221 code, and HORRIBLE gas mileage (13 mpg).

But I'd still replace the O2 sensor if I were you...

Good luck.

Erick

[monchichi]

Throttle position switch might be the problem.