I have every single o2 disconnected (I have 3 of them on my ODBII) and I only use the wideband with the MAP ECU. I didn't bother re-connecting the 3 sensors purely because my AFRs never changed and I still get oem gas milage (18-19mpg)
Could you? YES. However we need to find out from someone who knows about the OEM ECU. If you disconnect the primary O2, I am worried that the ECU may reduce timing and/or add fuel as safety precautions. Who knows what else it could possibly change. It may do nothing at all. But just something to think about.
I believe there are a couple of people toyotafan ? and MtFujitisu (Spelling)? that seem knowledgeable on the OEM ECU. Maybe they can help you out.
the reason I want to do that is just for the tuning, I will reconnect it when I done.
I need to find it out is what oem ECU will do if the main o2 is missing, yes, I'm worried it will add fuel for the close loop too.
right now I having hard time tuning the closed loop,because every changed I have make only appear on the wide band for couple of second before the it correct itself, so I don't know the change I made is enough, till I try that same condition again ( same vaccum and rpm) and my wideband don't have data logging, and the logging on the Map ECU suck big time.
maybe I just have to do the hard way. take it to the dyno is out the question ( 3 hour away)
even I try to tune it as close to 14.7 as possible? I know if i chande the closed loop will change the long term fuel curve ,but with the Map ECU you have to mess with the close loops, I'm just trying to get it as close as possible.