stock egt sensor (CCO) in JDM cat converter

[jtjerry]

So perhaps there wiil be more luck

I know someone of you are from aussie

picture below show stock typical egt sensor that is fit in cat converter in my soarer 1jzgte JDM engine. I am prety sure same (only TWO of them are in cats in stock JDM 1UZ V8 engines.

Is there anybody who know their purpose.
that sensor is pluged in ECU in pin that is named CCO

there is urban legend that say it is only for warning when you overheat catalityc converter BUT...

1. it is in place where not JDM cars have 2-nd oxy sensor...
2. we try simulate its resistance (as in service manual so cco pin in ecu will see around 2.5 volts) but it seems do not work (looks as ecu looking not only for right voltage but for changes too).
3. without it car seems run rich and ignition seems to be not where to be
4. idle seems be too low (550 RPMs, should be 750)
5. friend have soarer (Lexus sc400 with 1jzgte swap) as me. when it do not have that sensor he have same as me: big fuel consumption, very low idle, and ultra rich AFR almost you can feel gas in exhaust fumes so rich car was, looks as ignition timing was pull back too., after connecting that sensor everything is alright. but that is only my feelings

looks as without it ecu pull back ignition (lower idle) and ad much more fuel as required.

my theory is that sensor is as much important for engine as at least second oxy sensors in US toyota engines.

http://img155.imageshack.us/my.php?image=soareregtsensorrn8.jpg

anybody have any experiences?

 

[Peewee]

I'd guess that the issues you see with it unplugged is that the ecu is running in some form of 'limp home mode'

Similar fashion to unplugging a temp sensor.


EDIT: Purpose is just to sense when the cat fails and overheats.

 

[Peewee]

After some more thinking, I came up with this response on Toymods, that I will now cut and paste.





I can see one flaw in your theory.

I can confidently say that 99.99% of people who have done a conversion with a 1UZ, or any other Toyota motor that runs the CCO sensor, has NOT installed the sensor or any form of trickery during the conversion.
And 99% of these people have not had the problems you've mentioned.
And if they have, it has been for other reasons.


I personally believe that it is just there to sense when the catalytic converters overheat.
They are placed AFTER the cats, where as the o2 sensors are BEFORE the cats.

ECU measured the EGT through these sensors, and if it gets too hot (ie, your cat is now a red glowing mass), the ECU turns the cat overheat light on.


I think back in the early 80's the sensor was directly connected to the dash light, and was just a switch, not a sensor as such.

Anyway, my 2c.