Okay, rephrase...pulled in relay so red wire was at 12v so as to activate the OD solenoid. The shop said the red wire was supposed to have 12v for OD.
No idea what the temp sensor is doing. It seems that it is internal as no sensors are on the lines or the pan. Not sure how to check the sensor other than the ohm check that was suggested earlier.

 

Scanner that can read data, or, ohms change with fluid temp. If it always thinks it is 73*, it will never request O/D.

red wire to 8 pin plug supplies 12 volts to both O/D, and TCC solenoids. Those circuits are controlled by the PCM. It grounds the circuit to engage the solenoid. (think the red wire also powers Governor solenoid....)

 

Are you suggesting that the sensor is bad? If so, how deep inside is the sensor? Is it something I can do or not? Not afraid to pull the pan.

 

It's possible, and it would explain your symptoms.... I don't think the computer cares if the trans is 'too cold too long', like it does the engine.....

The temp sensor is part of the governor pressure sensor, so, once the pan/filter are out of the way, it's right there, easy to see/change.

Is that the problem though? Don't know. You might be able to drive the truck to the parts store, plug a scanner in, and see what it thinks trans temp really is.... it should be over 108 by the time you get there, unless it is right next door....... If it still shows a low temp... replace it.

 

If I do it by resistance,...How much should it change> Any idea?

 

Both the TCC and the OD solenoids should read between 25-40 Ohms. the Gov. Pressure should read 3-5 ohms @ 0 PSI. The temp sensor should read around 1000 Ohms @ 70F.

 

If the temp raises do the ohms go up or down and how far should they move?

 

Also, if the measurement is to be near 1000ohms is 1250 too much to begin with?

 

Service manual only talks about resistance at room temp...... (1000 ohms.) My take on it would be, look for a change in value, not so much a specific value. If the reading is the same from stone cold, to after driving it several miles, then you have a problem.

 

Cold 1250 ohms warmed up 1800 ohms. I guess that is not it.