4L80E lock up comand

[Inspector]

Here is something to chew on.
93 van vin "F" will comand the the trans to lock and unlock with an erratic check engine light but will not set a code. After about 5 miles it will be ok until an overnight cool down and then will do the same thing for 5 miles.
Possible hint at the problem--eng temp starts at 90* then up to 200* then back to 36* then to 88* as viewed on a Snapon breakout box. The temp sensor has been pined out (if it is the right one) and reads resistance normally through warm up and operationg temp. The TMC and prom have been replaced with no help. Question---Is there another temp sensor for the TMC that keeps the trans out of lock up till a pre-determined temp is reached that may be going in and out of tolerence during the warm up?
Denny :rolleyes:

[Inspector]

Just did some digging and found out that there is a temp sensor inside the trans on the valve body. It is called the TFT or trans fluid temp sensor. It appears to be looking for a set temp to allow for TCC lockup. Maybe probable cause. As for the funny temp readings I haven't got a clue.
Denny :confused:

[david]

I would check the thermous stat{ i need to go back to school} and see what the engine temp. is.
Engine temp needs to be 170 degs at least.
David

[Inspector]

As for the TFT sensor, it has been changed along with the updated harness to the all the electrical needs of the transmission.
The engine temp readouts on the Snap-on reader has me puzzeled. I will pass along your suggestion that the eng temp should be at least 170 degrees. Thanks.
Denny