Code P0712 on 2002 F150 5.4l automatic 4x4 been flashing for two years, dealer said temp sensor was bad, changed sensor and fluid, still flashing shows 380 degrees all the time, shifts in and out of OD while driving at steady speed between 30 and 50mph. Worse when cold start and on cold mornings. Shifts fine drives fine otherwise. any suggestions appreciated.

 

First thing they should've checked was the resistance between the positive and negative TFT pins at the trans connector.

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

If the resistance is correct then an overheating problem is there and it's not a sensor fault.

If the resistance is not correct, then the internal harness/board must be replaced as the sensor is part of that harness/board. A new bulkhead connector going to that board is also advisable while you're there.

Good luck.

 

We changed the sensor and the housing that it came in, I have always wondered if the new sensor or housing was bad and we changed bad for bad... I was going to try and ohm out the sensor at the wiring junction on the tranny but did not know which two wires went to the temp sensor. When it first started flashing I was pulling a trailer, I dont remember if the shifting in and out of OD was happening before we put in the new sensor, but has done so since we changed out the sensor. Thanks for the help greatly appreciated.