Yablo

Why does it have one and what does it do? does it change the way the trans shifts at various temps?

Is it used to control a thermostat to by-pass the cooler?

Also, why couldn't you tap into the wire harness and use it as the feed for a temp gauge?

mrvedit

As far as I know, the built-in trans temp sensor is only used by the PCM to detect an excessively hot temperature at which it switches to different shift tables and perhaps takes other steps to reduce trans heat.
I suspect this once happened to me at the track while hot-lapping and the engine would then not rev over 3500 rpm.

It does not control a thermostat - there is none. Some aftermarket coolers have their own thermostat for that purpose.

The sensor is only a thermsistor - the PCM applies a voltage on one lead and measures its resistance on the other lead. Taping in would likely throw the values way off.

Several companies make programmable gauges that connect to the OBD2 connector and can display any or all parameters including trans temperature.
Personally I use the HP Tuners scanner to log trans temperature when I am curious about it.

jimmyblue

iTrader: (11)

Trans fluid temp also indexes the force motor table,
although there doesn't seem to be much sophistication
there. Some vehicles have a profile, I've seen others
that are flat w/ TFT.

91foxbodygt

iTrader: (7)

Where in the transmission is the temperature sensor located? And does anyone have a part number? I believe mine is faulty and causing limp mode.

98CayenneT/A

It is read from the manifold pressure sensor that is bolted to the bottom of the valve body
https://www.gmtransmissionparts.com/...FZO2wAodamwPrw

RPM WS6

iTrader: (3)

Old thread, but since it's back...

In my experience, this internal temp reading is usually about 10° higher than what is observed with an external gauge using a probe in the pan. So, when referencing trans temp from this sensor via a scanner, the results can't be directly compared to folks using a probe in the pan. Just something to keep in mind when comparing readings to evaluate temp behavior or typical ranges before/after various modifications or cooling provisions.

However, I have not run this test on many examples so it's possible that the couple I've compared just had poorly calibrated gauges or insensitive probes, though I suspect that the more central location of the internal sensor would in fact produce a higher reading than would be seen in the pan - all else being equal.

Jays_SSZ28

iTrader: (2)

It won't cause it to go into limp mode. It might read high and go into limp mode but in that case it would be high from something slipping causing it to read high. If it's going into limp mode there is a fault that will leave a code.
Part number would depend on what transmission you have.

Yablo

Since I got a email for this thread I started, I will put closure to it... at least for me.

I was having problems dropping out of OD while cruising on the freeway. This happened only on hot days... (100+)

I had a trans-cooler mounted in front of ( literally on ) the radiator using the zip ties supplied with the cooler

after lots of googling and no answers , I decided to move the cooler off the radiator about an inch... voilą , NEVER had that dropping out of OD since.

turns out that the radiator was over-heating the trans cooler, forcing a limp mode and dropping out of OD.

If you can't make brackets, then maybe some makeshift spacers... none the less, never mount it directly on the radiator.

hope this helps other people who are searching for answers like I was

Happy New years

mrvedit

Thanks for the update to "close" your thread.
Your information will be useful to others.

BubaGumpShrimp

iTrader: (1)

The temp is also used for converter lock up.. Stock setting is 140... Under 140 and it won't lock up.

mrvedit

Please tell me where this value might be in HP Tuners.
I don't recall ever seeing it and my trans/converter definitely locks up below 100F trans temp. Or are you referring to engine temp? Still don't know where that setting would be.

BubaGumpShrimp

iTrader: (1)

Sorry, you're right, it is motor temp of 140 that makes it lock and not the trans temp.. Hp tuners doesn't have the setting in it but i did see it in ls1 edit,, i have both programs.