Assistance/Input with code P0751 3.4L Auto

Hello everyone, appreciate you visiting my post.
The patient:
2003, Toyota Tacoma PreRunner 4-door, 3.4L, Automatic, 144,000 miles, not 4 wheel drive.
History:
I purchased new with 3 miles on the odometer, and considered a part of the family. Pampered and yes, a garage queen. Doesn't like to get it's feet dirty, so trails, etc.
Except for the Bilstein 5100's on front & 5125's in the rear she's stock. No lift.
Just giving history here, not trying to start an oil war.....I have only used Amsoil full synthetic in the engine and transmission. Probably about 4 months ago, I drained out approximately 4.5 quarts of transmission fluid through the drain plug and replaced with new Amsoil. I do this about every 3rd oil change. I know it's overkill, but it makes me happy. Transmission fluid is red.
Transmission type is A340E (based on door jam decal).
Transmission filter has never been replaced.
The code:
So this past Saturday I ran some errands, and all was well.
I was changing the oil on my wife's car so she takes my truck. I "jokingly" (but seriously) said be careful and don't drive it like she does her car.
So later she comes back and says can you come out and look at your truck. It's making a beeping sound.
It was the Ultragauge throwing a P0751 code (Shift Solenoid A Performance Stuck-Off).
Of course my first response was "what did you do to my truck?". I asked if the truck drove any different and she said it drove fine. I cleared the code on the Ultragauge and it has not come back. I drove it Sunday, Monday and today. I can't tell any difference in the way it shifts, or anything. I also checked the transmission fluid level (while idling in Park) and it's fine.

My plan is to change the transmission filter (Thank you Tim for the video), which will also involve changing out about 5 or 6 quarts of Amsoil ATF.

Any other thoughts or ideas????? Anyone else received this code?

https://www.bing.com/videos/search?q=timmy's+video+on+transmission+filter&view=detail&mid=DBE0268EC30A4A23891BDBE0268EC30A4A23891B&FORM=VIRE

 

Giving myself a bump to see if anyone has experienced this code.

 

Hi Ben
Check this out
http://www.customtacos.com/tech.old...06toyrm/06toypdf/06rmsrc/rm2006ta/0260018.pdf

Proper diagnosis is the key to the flowchart above .
The problem has to occur twice while your truck is running in order to set a code .
If you scanned your ecm and this code popped up , the issue has occured at least 2 times since you started your truck ( ignition cycle)

What to do now ?

According to the diagnostic flow chart , the Techstream scanner is needed to manually test the operation of the shift solenoids .
Any chance you have a Techstream scanner ?

 

these transmissions are pretty robust but they are a bunch of moving parts. If it were me I would research the best trans shop in your area. I am saying this not to scare you but this is one of those areas where a guy who does this all day is best. The shift valve kits arent too expensive but you will need someone with trained eyes to look at the valve body... there are quite a few small rubber check balls that go in the valve body and when they wear they get smaller and smaller and dont do their job as designed. You can put a shift kit in her at the same time and firm up the shifts... not neck jerking shifts but better than stock. I would expect this to be not that expensive, 3 hrs shop time plus parts.

 

Thank you guys for the input