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Shifting Issues Suburban

Kmitchener

Kmitchener

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Location
Kendallville, IN
I have a 1995 k2500 suburban with the 6.5L and i used to have problems with it not shifting on a cold morning with little to no warm up. If I would wake up late and have to jump in and go. Now its stuck that way, any chances the new prom BXPY could fix my problem? I read that it fixes the cold start, but mine never shifts, its always in 2nd gear. I have had alot of problems with this truck as I bought it sight unseen over a year ago. Alot of electrical problems which im wondering if it could all stem from a faulty prom. It currently has the correct prom for the truck just not the newly updated one....

Thanks
 
Welcome to the site Kmitchener.

Any codes?
With codes set the tranny goes in limp mode,deleting the codes will get it going again till they set again.
How is the fluid look,mebby you need to drop the pan and change fluid and filter.
 
Not exactly sure what you mean but I did have someone come over with the computer that plugs in and pops up codes, said shift solinoid A was weak B was out, both were replaced, along with fluid and filter, i found a notice online about cold start non-shifting and being stuck in 2nd gear all the time. Mine is doing this and its also how it started out, and gradually went in and out for longer periods of time untill it was completely stuck in 2nd gear. The notice said that the updated prom inside the computer fixed the cold start non-shifting, was just hoping that someone had this same issue, just doesnt feel mechanical, seems electrical, but I am far from a mechanic. Is it possible that even after replacing them the tranny still believes they are out because the codes were not removed?? Ive never been around the plug in/code thing.
 
disconnect the batts for 5 min,that will clear the codes.
I don't know about the prom.

But i know that the tranny trough connector at the rear of the tranny can give problems,maybe have a look for corroded pins or oil in it.
And clean the grounds at the dipstick tube.
Hooking the truck up to a good scan tool might tell you more.
 
ok, will check all that out tommorrow, and look into finding someone with a scan tool, if i remember correctly the batterys have not been disconnected since the solinoids were changed, the guy that changed them im about sure he would dissconnect the batterys before tearing into the tranny, but not quite sure to be honest. Thank you for your help.

On another note does anyone know why or how the ECM can loose power sometimes? I have to have a toggle switch hooked into the fuel pump and the ecm because sometimes the fuse panel under the hood, half of it dies for awhile, sometimes weeks. then will snap back to having power where i dont need the have the toggle switch. It is the most confusing thing i have ever messed with in a vehicle. Normally its broke or it works. This thing is so off and on....
 
Your transmission is electronic. If half the fuse panel goes out...

Bailing wire will not fix electrical problems. You have to take it apart and trace down the bad connection or wire. No way around it. Age and corrosion both take a toll on the electrical systems. It is possible to have a wire that has failed open by internal corrosion - I didn't say electrical was fun to fix.

Start with the grounds. Then pull the batteries, test them both and check the cables for corrosion. Next I suspect you will have to pull the fuse panel apart and clean the corroded connectors in it.

I am not sure if the 1995 still has the separate shaft speed sensors, but, these wires are known to have the insulation fall off them and short out. Bison had good advice for checking pins that can show up as solenoid codes.

Last PM member buddy on here for help with the prom as he knows them inside out.
 
thank you all very much, looks as if i have plenty of things to try before i buy the updated prom. any more input is appriciated, im just a newbie to these and just need it to run, its my only vehicle
 
If your interested I still have an almost brand new ECM with the updated 95 SUBURBAN prom in it sitting out in the shop. It had less than 500 miles on it before I swapped to the DMAX. The updated prom chip was to address teh slide bump 1-2 shift, but stuck in 2nd is limp mode. You need to get a scanner hooked up when it is doing it and see what it is commanding.
 
The PROM can cause random fits like this, but nothing consistent that I have ever heard or experienced and I have run BPAC 95 suburban PROM code quite a bit although with modified pressure and shift parameters. And a key cycle should resolve the PROM error, even if codes were stored in history. I suspect this is not a PROM issue. It could be a wiring issue.

When the solenoids were changed out, did you do them all or just the shift solenoids? A bad Pressure Control Solenoid (force motor) may not code but cause a lot of other codes because there wouldnt be enough pressure to shift. When in there best to replace them all, since the PCS and TCC solenoid are most common 4L80E problems. All of the solenoids can be found for like $140.

Also if its possible that the wrong PCS solenoid is in there, like if a 92 or 93 4L80E was ever transplanted into it, or somone changed the PCS to the older version that works different than the 94+ years trannys. Need to check tranny pressure with a gauge into the test port of the tranny, compared to what scanner says PCM is commanding.

Your fuel lift pump is likely on a switch because the Oil Pressure Switch/Sender has failed, which is what sends it power when the engine is running. That is very common, unrelated to the fuse panel issue. And have you verified that half the fuse panel actually loses power, and is that the ignition power part compared to the battery power part? Bad ignition switch is common and sounds like maybe previous owner bypassed the ignition switch to give power to all the necessary stuff.
 
getting a code scanner tommorrow, went through alot of grounds today taking apart and cleaning, mostly in the motor compartment. any well known grounds under the truck? looked around as best i could but shop light was broke, getting a new one tommorrow and hope to get something accomplished with code reader and a light to see what the heck im doing under there.
 
Code scanner reads only codes,you need a bydirectional scan tool.
codes on your truck can be read using a paperclip connecting the top right 2 pins of the OBDconnector under the dash.
With Key on it will flash the codes with the SES light
 
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