Water Temp Sensors

[landtoy80]

I see three water temp sensors next to the thermostat.
I only find one water temp sensor in the Toyota Supra Manual and that the single wire water temp switch.
The other two are two wire sensors. What do they control and how do I test them?

Reason for post is I want to test the temp sensor for the trannys overdrive.

 

[zurud]

One for ecu, one for gauge and the other one for turning on the auxillary fan. I guess if anyone of them don't work then it broke.

 

[Nick M]

http://www.cygnusx1.net/Supra/Library/TEWD/MK3/manual.aspx?S=Main&P=023

Shaeff and Jdub have both posted a photo with the description if the E3 description is confusing.

 

[isnms]

 

[landtoy80]

So which one would control the auto tranny?
Would it be the ECU temp sensor?
How do you test them? Cross the two terminals or test each terminal to ground?

 

[Nick M]

Shorting the connector will simply read normal operating temp. Unless JJ says different. But I am pretty sure it is an NTC type thermistor.

I don't have my book here, but the engine control unit(TCCS) sends the signals to the trans control unit. The online EWD shows 4 colored wires, IDL, and speed sensor as inputs. You will have to check the wire colors yourself.

 

[jetjock]

It won't. It is.

 

[Nick M]

If there is no resistance, shouldn't it show hot? Besides a code for open or short.

edit:never mind, it will substitute a known good value.

 

[jetjock]

Sorry Nick, my bad. Is this the gage we're talking about? If so yeah, it'll show hot but hot isn't normal. Or are you talking about the ECU coolant sensor? If so yes, a short across it will default the ECU to hot (normal) temp. That ought to confuse him

 

[Nick M]

I think his car shifts into O/D sooner than he thinks it should. No, not the gage. He mentioned crossing the wires, so I assumed he meant the two wire harness behind the powersteering resevoir.

 

[jetjock]

Ah, I see. I'll have to defer to your expertise about what the auto does based on coolant temp because that's one area I've never looked into. I'm a manual.

OP: The sensor can be checked according to the graph published in the book. As Nick said it's NTC and iirc will be around 200 ohms when the coolant is at normal operating temperature.