[xtreme off-road]

Anybody have time to run a little experiment?
When it comes to the new OBD II vehicules we all know that if you remove your catalytic converters it will set a code because the second O2 sensor can "see" the same exhaust as the first one.
My experiment is... what would the computer do if you crossed the second sensor, on a dual cat systeme, from side to side and removed the cats. The second sensor would "see" a different exhaust than the first one because they are rossed. <img src="graemlins/crash.gif" border="0" alt="[crash]" />

Just a thought that might actually work. Give it a try and post your findings. It may be the first step in getting more performance out of these OBD II vehicules.

[dmorris1200]

That would most likely not work. The computer looks at the cycle rate of the sensors not whether or not a sensor mimics another. The computer knows that the upstream O2 sensor cycles at a specified rate, measuring the constant shift from rich to lean exhaust. The downstream sensors don't see this constant shift because of the effects of the cat. converter. When the computer see's the downstream sensors start to cycle (not just copy the upstream sensor) it knows the converter is not doing it's job and sets a code.

[Necro]

they actually make a plug in sensor for this. summit sells them . after removing your cats , plug this is and it will trick the computer into thinking its seeing the o2 change.

but connecting the upstream o2 and the downstream o2 wont work. they are actually different so it would not work. plus the second also sees the temp increase caused by the cat.

[dmorris1200]

Well I can't speak for all manufactures out there but I know Ford O2 sensors basically have four wires. Two of them are for a heater element which is used to heat the sensor allowing it to cycle quicker therefore allowing the PCM to go into closed loop operation quicker. The sensor must reach a certain temperature before it will cycle, hence using an electric heater element allows it to cycle quicker which in turn allows closed loop operation quicker which, for car manufactures, equals lower emmissions. The other two wires simply tell the computer the voltage of the sensor which varies between .1 and .9 volts. I have never seen a PID display for any O2 sensor showing exhaust temperature, only sensor voltage to monitor cycle rate.