Checking the Transmission Fluid Temperature Sensor. There is a reason for it. The sensor can Skew. I said skew. a skewed sensor will mean either the computer thinks that the fluid is either too cold and thick for shifting or the computer will want to go into hot mode. Hot mode means no OD. Overdrive. Overdrive means no mechanical coupling.

Use an infra temp gun. There are two windows to a typical gun. the top window is the laser. It gives you something to point with. The bottom larger window is the infra red. This is what actually takes the temperature. Nowadays they are getting cheaper than dirt.

Place the gun on a hot transmission cooler line and record the reading.

http://i120.photobucket.com/albums/o187/USMILRET/4L80E%20Transmission/DSC02611.jpg

http://i120.photobucket.com/albums/o187/USMILRET/4L80E%20Transmission/DSC02612.jpg


Aiming the temp gun on a transmission at operating temperature will give you the temp.

The transmission fluid temperature sensor is the gray thing strapped to the wiring. It is called a thermistor and bathed in transmission fluid.

http://i120.photobucket.com/albums/o187/USMILRET/4L80E%20Transmission/Newtrans095.jpg

The key ingredient in all of this is of course this chart. You have a minimum, normal and a maximum column,

http://i120.photobucket.com/albums/o187/USMILRET/4L80E%20Transmission/TFTResistanceChart.jpg

How to find the pins to test with a multimeter. Go for Pins L and M using Ohms resistance.

http://i120.photobucket.com/albums/o187/USMILRET/4L80E%20Transmission/threeimagehomework.jpg

Use this type of probe but not the male type as shown. Buy the female type for the transmission. I would buy two of each anyway male and female.

http://i120.photobucket.com/albums/o187/USMILRET/4L80E%20Transmission/IMAGE_6301.jpg

Temp guns are good for checking engines vs OEM gauges, brakes, radiators, bearings, insulation in walls, around doors and windows. Even driving the cat into the glass door.
However I think dogs will develop that stupid permanent look straight into the ground. :)