A lot of sensors only have a 5 volt reference signal from the computer…
But a good scanner is the best way to see what’s going on, they are used for more than reading codes… My buddy (and someone I am mentoring) has a really nice $7,000.00 scanner that can do all kinds of stuff… lol Mine is only a cheaper $400.00 one… But the difference in what all he can do with it is very helpful… But you also have to know and how to use it…
Lots of good ideas given here, thank you all. I’m going to take this to a shop, hopefully next week.
As a bit of follow up, I took it in and there was a code logged. It referenced the fuel pump relay. Checking that showed the relay was loose. That was corrected and, so far, the issue hasn’t returned.
At that mileage, that is the best repair you could have hoped for.
Now, take car of that transmission before it is too late.
They might power flush it and ruin it.
The only thing that makes sense about keeping old fluid is that there is grit in there that helps the old transmission work. But this is only when the transmission is at the end of its life.
Does changing fluid pick up new sediment and then deposit it somewhere else? Maybe that’s what happens. If that’s the case, then take off the pan and clean the thick layer of sediment off of it. Then change the fluid again after 100 miles or so.
That is why I recommended taking to a dealer or transmission shop to evaluate the condition of the fluid and trans…
As the friction material wears it mixes with the fluid and can continue to keep the trans shifting normally, and a transmission can go for a very long time like that… Heat is what truly kills a transmission… I have seen a ton of fleet vehicles that never serviced the transmission go 200 to 500K plus miles, then again I have seen state trooper vehicles that change the trans fluid every 20K miles die around 90 to 120K miles… Again I always recommend the proper service of your vehicle but if the trans has not been serviced and you do it late in the game you are flipping a coin as to if it will work or not…
The “sediment” builds up in every nook and cranny of the trans including all around the valve body, and there is a lot in and around the planets, drums, pistons, etc etc etc… Transmission fluid is a detergent…
The best way is to flush and take the pan off and replace the filter (if able)… If that sediment makes it to a spool valve that is moving it can stop it from moving and damage (slowing down or reducing the fluid pressure causing slippage builds up heat) the trans as well as the many very small orifice/passageways in the clutch drums etc…
I removed a thick layer of sediment from a Toyota transmission pan, and changed the fluid. Then 5000 miles later I did it again and there was a thin layer on everything, including the pan. 5000 miles later there was no film of sediment on anything. So it took two changes for the ATF to not be saturated to the point where it’s leaving a film on everything.
Toyota Transmissions are almost bullet prof anyway… lol
Heck I built a Volvo RWD transmission years ago that was nothing more than a Toyota Celica RWD trans… The valve body was different but I used a kit and converter for a RWD Celica trans to build the Volvo trans and they were the same…