2QUIK6

In trying to find my surging all the time problem, I disconnected the O2 sensor. Surprisingly no codes were thrown and so far one short trip, and no surging, but it would occassionally run fine before, so only a few more trips will tell for sure.

Anyway, I did notice on the scan tool that it now stays in OPEN LOOP all the time and the O2 voltage, even though its disconnected floated around between 430-450 mv, anyone know why this is??
Or is this when there is infinite impedence, much like running very rich?? ...but since it stayed in OPEN LOOP no BLMs were adjusted and the "histogram" in Datamaster just showed everything perfect, not rich or lean....
I might add this is a 3-wire heated O2 if that makes a difference.
Thanks

hectorsn

The ecm is working just like it's supposed to. That's what it does when the o2 is unplugged. There is a reference voltage of about a half volt, 450 mv. Without the o2 plugged in it won't go to closed loop. Since closed loop is what changes the BLM, no BLM change, just like you noted.

2QUIK6

Thanks hector, thats what I was suspecting. FYI, after prolonged driving to work, I did finally set a code indicating "left O2 failure" but maybe thats because I'm running a 3-wire heated O2.

tpivette89

i had mine disconnected while i was driving to work (about a 15 minute drive) and suprisingly got no codes either. i thought something was wrong with my ECM. if its happening to other people, i guess not

hectorsn

Naaahhh, the heated o2 and the one wire ones are the same thing to the ecm. Only one wire of the 3 or 4 wire o2's goes to the ecm anyhow. It's hard to tell which car it is you are referring to from your sig and I figure it aint a 3rd gen if it has multiple o2's. ANyhow, before OBDII, the ecm wasn't programmed to concern itself much with o2 error codes. If it got to the BLM limits either rich or lean, it would spit an o2 code, either rich or lean. That's about it. Now OBDII has codes for rich or lean or shorted or open, and even codes for the heater circuits.

2QUIK6

You got me how this thing is wired, this was in my TPI powered truck, I had Fuel Injection Specialties wire the harness for me using part of the original TBI truck harness, so they used the O2 from it. It had only 1 O2 sensor originally, and still just has 1, so I don't know why it there a code saying "left O2 failure", and this is using DataMaster 8D for the 92 TPI. Anyway, seems to run fine without it hooked up for now, except idling, so I'll leave it until I can figure out why its surging so bad at all rpms and load when its hooked up.