Installed o2 P0140? [Archive] - Forum


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07-28-2009, 02:52 PM
Ok so I had a new cat installed on my car....and I guess because it wasn't an exact replacement for the factory one, my check engine light came on. I replaced the o2 sensors and that did nothing. I kept getting the cat efficiency is below threshold I bought an o2 sim for the downstream position.

I hooked it up, cleared the codes....then drove for about 200 miles with no problems. Now all of a sudden the mil comes back on and this time I'm getting the P0140 activity on the downstream sensor.

I did search some old posts and that helped a little....but none of them really said what I can do to fix this. Oh and another thing....when I did that last scan, it said that my heated oxygen sensor is still not in a ready status. Could I have a bad o2 sim?

I live in the wonderful state of IL where you cant renew your plates unless you pass I'm kinda screwed right now. My plates just expired.

Any help would be appreciated....


07-28-2009, 03:59 PM
The O2 sim should prevent the code from popping up. If its not that either means you got a bad sim or the wiring going back is shot. Your best bet right now is to either pay a tech to fix the problem or find someone local with a tuner to delete the code. I think the second option is your best bet. I don't know of anyone in Chicago, but if you can drive to Round Lake, IL to visit Mark with MP Racing he can fix the code for you for a nominal fee of some kind. I have no EGR and for all intensive purposes no rear O2 and I passed my emissions with flying colors so I know for a fact that he can get you to pass. The only concern would be him having the time to do it on short notice.

07-29-2009, 04:50 PM
Thanks for the reply.

I'm starting to think that the o2 sim is fine now....or maybe its half working. I drove another 30 miles and now the check engine light is off. I went by the testing facility today and passed, so I'm all set for another two years.

The heated oxygen sensor monitor still isnt in a ready status, but I guess it doesnt matter.