96 4R will not shift into Overdrive

[Renegade_Medic]

Howdy,
Need a good tech answer or some ideas.
1996 3.4L 2wd, will not shift into OD.
I just picked it up and am unsure how long this has been happening. It did go into OD at one point on the highway after about 20 minutes of driving. I was stopped at a light and turned on ECT and OD off and then when I shut that stuff off at speed it shifted into OD with no issue and held fine with no shudders or anything. It shifted into and out of OD without issue for the rest of that drive. Since then, it has not shifted into OD at all, probably about 1.5 hours of driving that should have been in OD.
Things I've checked so far:
Trans fluid was about one quart overfilled, drained to correct level. Also, added some Lucas trans fix, seeing if maybe it would help. No change from either of those.
Coolant is at correct temperature both indicated and on the OBD, meaning it's not stuck in cold temp mode.
Throttle Position Sensor was mapped with OBD logger and was smooth and linear, no issues there.
Fuel trims and everything overall looks good.
Obviously, no codes.
So does anyone have any ideas? ECU? is there some way to tell what gear is being commanded by the ECU or force it into a certain gear?
Thanks!

 

[19963.4lsr5]

One thing to check is the TV cable adjustment and ensure its connection at the trans isn't sticking.


Sent from my iPhone using Tapatalk

 

[Renegade_Medic]

One thing to check is the TV cable adjustment and ensure its connection at the trans isn't sticking.


Sent from my iPhone using Tapatalk

Ok, I did verify the adjustment on the throttle body and it seems free, but I'll take a look at the trans end as well.

 

[Renegade_Medic]

Fixed

To add some closure to this thread, it was actually the PCM.

I looked into the transmission temp sensor and it looks like a pain to get out.

I noticed that the OBD reader was not giving me a speed while moving. I confirmed with my dad, who also has a 96, that they do in fact show speed on the OBD. I swapped the sensor for a known working one and it didn't change the shifting and still didn't register the speed. Getting closer.

I decided at this point that I should try a computer, as I can get them for cheap from the local junkyard. [MENTION=159759]Spunky1[/MENTION] and I headed out to the yard, which was pretty slim, but chock-full of PCMs. I grabbed one out of a 97 and installed in the parking lot.

It worked, everything works as it should, no codes, and the OD works perfectly.

However, the OBD still isn't reporting speed so I'm not exactly sure what is going on with that.