Hello again! I posted here about a year ago because my transmission wouldn't go into park. Well I've fixed that! Swapped out the transmission valve body in the process because it was actually cheaper to get a new valve body with new sensors than just buying the sensors themselves ​ plus the valve body was rebuilt with higher quality parts.


Well on my way into the transmission I figured out why she wouldn't go into park, the second gear band anchor fell into my park pawl rod. After inspection of my my band and drum I've determined the band is pretty much shot and very far past its adjustment point (explains why I lost 2nd gear haha) the drum actually seems to be alright. Well I was a dummy and didn't grab a slip in band when I did the job but I've got one on the way now!


In the mean time I've been dealing with a few problems. So I've got the second gear adjusted to spec (even though she's pretty gone, she does actually hold) and it grabs but i've been fighting with this TV cable, before I had to absolutely mat the gas and let off to shift the truck, but after adjusting the throttle (gas pedal) cable and the TV cable I've gotten to a point where with light gas all the shift points are dead on 1>4th gear but when I mat the accelerator to speed up quickly it won't shift out of first, after shifting to neutral then back to drive while driving it'll pop into 2nd but then just kinda stay in 2nd. No down even if I stop just kinda stays in 2>4th gears. won't even go into 1st if I pop it in neutral or any other gear lol


So to add to this complexity after fiddling AND flicking the TV cable just a hair trying to find that sweet spot I FINNALY GOT IT. Shifted 100% like factory for 2 days straight thhheeeennnnnnn CEL. Good thing I work at a shop with neat computer tools because i figured out the code was for the governer pressure reading more than 0 at 0mph wellll that's what the code said but the on screen diagnostics say otherwise, I reset the CEL and took the computer with me on a test drive, the sensor was telling me the pressure was 100% operating to spec but the CEL came on again... During the test drive where everything was working perfectly on screen? It never read over 3 at 0 and that's what the CEL is coming on for?


​​I'm going to be dropping the valve body again at the shop to install a slip in band, anything I should check/get that could pretain to this issue or do you think getting a healthy 2nd band in the truck might possibly solve this issue? I just replaced that valve body so I don't want to have to keep throwing more and more parts but I guess I have to if I have to hahaha also I have emissions in 2 months so I gotta fix this soon lol


I forgot to mention the O2 sensor plug was found melted on the cat lol previous owner didn't put the wire clip back (I honestly don't know how it passed emissions like this but it did....) This ended up frying my pcm so I got a new pcm reprogramed then rewired the O2 sensor. I hear the O2 sensor can cause issues with the pressure sensor because they use the same ground. Can I ground the pressure sensor elsewhere on the vehicle entirely separate from the O2 sensor? Is that possible to do from the transmission wire plug? I fear that ground rail might have some electrical noise due to the O2 frying lol.


I know it's a lot I'm just trying to dump the info I have, maybe you guys know what's going on with it lol because it seems like a lot of fu**ery damn near bout to replace the whole transmission but if the O2 sensor is the real problem that wouldn't fix my issue anyway

 

I don't know if they share a ground, but, they do share the source for the 5 volt reference signal..... that circuit shorting out can cause some interesting issues.

These transmissions were famous for not wanting to shift at WOT...... I don't know if there even IS a fix for that. Maybe changing the trans pressure sensor.... but, yours is already new.....

 

I've been reading around and aperently they both share the ground thats attached to the block at the power steering pump. I actually ran 4g wire from There to the body in hopes that it'd reduce some noise but I'm still having the same issue lol.
I think I'm going to figure out if I can ground the the sensor somewhere else and maybe at the same time I'll tap clean 5v from another location as well. Know of anywhere in the truck I can tap 5v from that isn't a cigarette lighter? lol


Found this Lil diagram online which will help me out a bit.
(back when my pcm blew I had to run 5v from a phone charger to the TPS power wire just to start my truck ​​)

 

I think I'm going to rip apart a 80+ gold computer power supply and make my own switching 12/14v > 5v step-down converter to supply my sensors with a clean 5v and not use the ****ty linear step-down converter than comes with the PCM. I've heard that this PCMs step-down converter has a lot of issues with noise and wrong voltages. I'm fairly techy so it shouldn't be all that hard. I'm going to go through with the 2nd gear band install first to see if that could be my issue, I think the band being way out of spec might be causing an issue with the pressure but at the same time everything seems to be reading beautifully lol

If I end up doing this I'll make a full write up on the process for future users. I might even be able to use my old "junk" PCM if I do this because that's the only part that blew. Maybe writing this up will save some people $400 getting and reprograming a new pcm.

 

Strangely enough the CEL went away after driving but comes back after any time I do a reset on the CEL. My best guess would be that resetting the CEL resets some value in the computer that sets its own values while driving? After a day or so of driving the CEL go's away and doesn't come back unless I do a CEL reset with the shops computer. Going to go through with the band install like stated before and if the CEL comes back I'll do some driving to see if it permanently go's away. If not I'll continue with the botchy power supply job lol

 

idk if adding an external power supply would work, in fact it could easily make things worse. The PCM looks for a value across the sensor which is usually a voltage drop, in order for that to work both sides of the circuit have to hooked up to the PCM. IDK if the PCM measures the voltage going out (i honestly think it should, just to be sure the voltage regulator is working as designed) or if it knows what its supposed to be and just measures the return voltage.

In the first case you will have to tie your power supply into the PCM (at each sensor feed line, while i dont think each sensor has its own feed there is going to be more than one) in order to have any chance of it working.