Temp sensors, whats their purpose ?

[COFFEE]

Does anyone know?
I have been told the Temp sensors after the cats on the sc400 are to monitor the performance of the cat.
When the cat gets blocked the temp rises and the sensor activates the warning light on your dash.
But is this all it does? somebody further told me it works with the ecu and assists in adjusting the mixtures ?
Does anyone know foreshore ?
I have a mate who fitted a 1uz-fe in a hi-ace, when it went for the pollution tests it failed because the co reading was 1% to high.
The van isn't running the temp sensors and was wandering if the the temp sensors really did play a role in the mixture, maybe this is the problem ?

Any assistance would be greatly appreciated.

Regards

Stephen

 

[gloverman]

Hello Stephen

I hope to convert a hiace van. What model did your mate use, some more info would help. Is your mate using the O2 sensors in the exhaust( at the front in the headers) and is he using the standard ECU?

 

[COFFEE]

Gloverman,
I am not sure of the model but it's a Hi- ace as well.
Standard crown engine with standard computer.
Using all the stock bits except custom exhaust without the Temp sensors only.
Co2 sensors are being used.

Regards

Stephen

 

[MaxPower]

The temp sensors are used for over-temp protection of the cats. In a lean condition (such as decel enleanment or lean cruise) the cats can get too hot and fail. The ECU will cool the cats by adding fuel for a short period or decreasing the amount of decel fuel enleanment or delay the onset of decel fuel cutoff (while slowing down the ecu is still adding fuel for a short amount of time). There are also other ways the ECU protects the cats. This is also assuming they are temp sensors - your not getting them mixed up with the second set of O2 sensors?? I have never looked at a complete exhaust system of a SC400 so cant really tell you what they are.

 

[COFFEE]

Maxpower,
Me personally, i probably couldn't pick the two apart ?
I know of them from when i replaced my exhaust system from the cats back.
When i drove it out the light on the dash was on, when i questioned it, the exhaust guy showed me the two sets of sensors and explained what they do.
My mate has put a 1uz-fe in a Toyota Hi-ace van but its not running the temp sensors.
Someone had told him what you had just said, he thought by not having them connected maybe the ecu was making the mixture richer ?
Hence the questions, the only other thing we were thinking is maybe the air con not being connected may have something to do with it ? it's also idels high.

Regards

Stephen

 

[Zuffen]

Coffee,

I don't run the temp sensors or air and mine seems to run well.

PM me and I'll give you an engineers name who may be able to assist.

 

[jtjerry]

arent they seconds o2 sensors? when I looking at schematisc they still have 4 wires as normal main o2 sensors and still are named in service manual as sub o2 sensors...
I am wonder what is happen when you remove cats...

 

[Zuffen]

If you look at KDogs schematics on the Crown one of the items on the engine diagram is an exhaust temp light. There's also the exhaust temp flap mentioned.

I suspect it's all to do with EGR so we shouldn't see it on any 1UZ in Australia.