What is the transmission fluid temperature sensor (TFT) reading? In general it will take an ODB2 scanner capable of reading more than generic ODB2 data. IMO this is the first step to trouble shoot. You don't know if the TFT sensor is:
- Shorted (to ground or power)
- unstable. This indicates a loose connection.
- or simply out of range.
The Ford service manual calls out Pinpoint test "B" that basically starts out by see IF the TFT is sending anything at all. Then next it goes on to voltage and ground measurements that are designed to narrow down IF this is a wiring issue or sensor issue. IE confirming there is voltage at the TFT supply and seeing if the TFT's resistance matches a reasonable value depending upon the current temperature.
IMO it's silly to attempt to replace the TFT without determining IF the sensor is bad before hand. Plus the TFT sensor is part of the transmission harness which will require the whole internal transmission harness to be replaced.
Transmission Fluid Temperature °C °F Resistance (Ohms)
-40 to -20 -40 to -4 967K - 284K
-19 to -1 -3 - 31 284K - 100K
0 - 20 32 - 68 100K - 37K
21 - 40 69 - 104 37K - 16K
41 - 70 105 - 158 16K - 5K
71 - 90 159 - 194 5K - 2.7K
91 - 110 195 - 230 2.7K - 1.5K
111 - 130 231 - 266 1.5K - 0.8K
131 - 150 267 - 302 0.8K - 0.54K