P0140 code question?
 

So, I finally got all of the exhaust done, put an O2 simulator on, and now after driving for a few weeks have an ses light with a P0140 code. Whatcha guys think? My car isn't running any different, so I assume it is the O2 simulator. If it was a fuel problem, or something else, wouldn't it be obvious? Any advice?

Whcih motor do you have?

I think the downstream (behind the cat) O2 is very common with exhaust change but I thought it was P0141, or P0142 :wacko: :huh:

I have the 3400. I put an O2 simulator in place of the downstream O2 sensor.