O/D Light Blinking, Check Transmission in Message Center

[weburt]

I have a 2003 Eddie Bauer Explorer with 204,000 miles. All freeway miles except for occasionally pulling a single axle trailer with < 1000 pounds on it.
The only parts changed so far are tires, alternator, and all 4 axle bearings. This is a great truck/car.
Last week, the O/D light started blinking and the message center said "Check Transmission". Here are the steps to reproduce:

1) Turn on key (no blinking light, no message)
2) Start car, put in any gear. Still no light or message
3) Put in drive - and drive ! Still no light or message
4) Drive around 4 to 10 miles at any speed - Light will blink, message appears
5) Stop. Start driving and count the shift (there should be 5)
6) All 5 shifts occur where they always have. No slipping.
7) At speed (in gear "5" - I know it is not a "gear") push the O/D button on shift lever - car "downshifts" (higher RPMs). Push button again, car "upshifts" just like it always has.
8) For remainder of drive, O/D light blinks. Message center resets and message does not come back.
9) Turn car off. Restart car, no message.

Any comments would be appreciated. The car has slowly gone from 21 MPG down to around 19 over the last 2 years, but other than that it does the 100 mile round trip perfectly. No weird tire wear, no unusual noises, no difference in shifting. I have never changed the transmission fluid, because my previous 6 Explorers have not responded well to fluid and filter on the tranny. Regular maintenance is done on all other parts without issue.

 

[PopRichie77]

You need to get the trans DTC code pulled, it sounds like the Torque Converter is not locking.

 

[statenvc]

Where is the torque converter located and is that something that I can fix myself