What is this device ? O2 or "Exhaust Temperature Swit

[Hendrik]

Dit some time ago a downloas from this site about a 1986 XT turbo.
It fits remarkably well my 1986 turbo wagon. Seen there a
"Exhaust Temperature Switch" is it the one on the picture or is it an O2 sensor ?
What is the purpose ?
On the general electrical engine electronics no more any mention or reference.
The heat tip is about 3 mm thick an goes where I would expect the o2 sensor , directly after the turbo an in the beginning of the cat.


http://www.ultimatesubaru.net/photos/sh ... 500&page=1

Thanks for input............

[Gremlins]

Interesting, my EA82T has 02 sensor and exhaust temperature sensor but it doesn't have a connector that looks like that!! From your description of the location of the sensor it sounds like the 02 sensor that you are talking about.

The exhaust temperature sensor on my vehicle is located on the bottom of the catalytic converter, (see picture below) and the 02 sensor is between the turbo and the cat converter as you described. Hope it helps you work out what you're looking at.

Also, not all turbo's have the exhaust temperture sensor so you may not have one.

[Hendrik]

Interesting, my EA82T has 02 sensor and exhaust temperature sensor but it doesn't have a connector that looks like that!! From your description of the location of the sensor it sounds like the 02 sensor that you are talking about.

The exhaust temperature sensor on my vehicle is located on the bottom of the catalytic converter, (see picture below) and the 02 sensor is between the turbo and the cat converter as you described. Hope it helps you work out what you're looking at.

Also, not all turbo's have the exhaust temperture sensor so you may not have one.

Thank you ,
I still do not know what the function is of the temp. sensor .

May be there is a second sensor somewhere (O2 sensor ?) , I will have a look tomorrow. On your picture it seems the same sensor "feeler" , which comes out of the device on my picture....
It only is mounted on top of the cat and not downward as in your case.

My concern is , that I may be have to change the O2 sensor dus to fuel economy , but where sits the thing ?

Thank for your reaction , coming back on it.

[Hendrik]

I forgot to mention that the device is "Hitachi TWG-1"

[fredsub]

my ea82t had that too, and never figured out what it was (until now )before replacing the exhaust system...could never get it out either......
as for purpose?.......
Sure the cat needs to operate at a certain temperature, ~600degC I think,
but without that sensor signal, what does the standard ECU do?

[Gremlins]

I think I remember reading somewhere that the exhaust temperature sensor was fitted to european EA82T's (and obviously also some Japanese models as that's where my motor is from) and it's function was to prevent excessive exhaust temperatures in the event of sustained high speed motoring (I guess that might happen during a run down the autobahn or something like that). If this sensor is activated it turns on a warning light on the dash and also signals the ECU to enrichen the fuel mix which apparently reduces the exhaust temperature. (it will also make your motor drink fuel like it's going out of fashion).

Hendrik, the 02 sensor should be alot fatter than the exhaust temperature sensor. It's (from very rough guess) about 20mm diamater with a single wire coming out the back. I haven't got a photo of that one to show you unfortunately, but I think they can be located in different places depending on where the EA82T is from.

[Hendrik]

I think I remember reading somewhere that the exhaust temperature sensor was fitted to european EA82T's (and obviously also some Japanese models as that's where my motor is from) and it's function was to prevent excessive exhaust temperatures in the event of sustained high speed motoring (I guess that might happen during a run down the autobahn or something like that). If this sensor is activated it turns on a warning light on the dash and also signals the ECU to enrichen the fuel mix which apparently reduces the exhaust temperature. (it will also make your motor drink fuel like it's going out of fashion).

Hendrik, the 02 sensor should be alot fatter than the exhaust temperature sensor. It's (from very rough guess) about 20mm diamater with a single wire coming out the back. I haven't got a photo of that one to show you unfortunately, but I think they can be located in different places depending on where the EA82T is from.

I did inspect the cat (vertical part of exhaust m directly after the turbo) ,
no more sensors ..............Just the one formerly described.
On the picture yoy can see two connectors , both 4 pole. The connector to the harness is a typical subaro connector , the other one on the sensor side is not (hitachi typical?) .In fact the intermedia piece between the 2 connectors seems just an extension to fit to the right connector.

I did measure the harness side and sensor side electrically ":

4 connections , 1,2,3,4.

Sensor :
Between 1-3 = 50 Kohm
between 3-4 = 160 Ohm
all at cold temperature

Harness (ignition off)
2-ground =700 Ohm
1-ground = 1400 Ohm
3-ground =80 Ohm
4= ground

Voltages at harness (ignition on , engine running/not running =same)
toward ground

2=5 volt
1=12 volt
4=ground , 0 volt
3= no voltage

I hope this helps to identify the part.......
Stiil cannot very well imagine that there is no O2 sensor at all !

Any comments , help are welcome...

[fredsub]

The O2 sensor should be on the header pipe just under the turbo, not on the pipe to the cat. You may not see it, especially if someone broke it, or there is
just a bung there....then you have to feel for it.