Need help ASAP!! Stummmmppped!

[Sierra3500HD]

2008 GMC Sierra 3500 HD 200k

Banks Super Scoop
EFi Live
3.5" MBRP

Little bit of a story behind my issue it all started 2 months ago throwing P0276 selonoid c stuck "on" took the truck in for repairs "replacing the selonoid" shop did replacement with issue still there they went ahead and did the valve body and all the selonoids. Problem was still there shop informed me that transmission needed to be rebuilt. I told them to go ahead with the job only to find out the problem was still there. Barley got a few days out of it to find out the rebuild was done improperly and actually blew it up. I pulled my truck from the shop to goto another transmission shop. So this shop put in a used tranny with 30k on it it's now been off the road for 2 months after the re and re all electrical has been checked with no result at this point I'm fed up truck has new tranny and no one can find the issue with the same code any help!!?? Anyone!!!??

 

[Mike L.]

Never heard of a P0276.

 

[clrussell]

External wiring? I've had 2 now.. First one took me 3 days straight to find.

How I found it on the one yesterday look at the pressure switch that's active for that gear, In my case it was ps3. Truck not running showed ps3 on, unplugged valve body and ps3 still stayed on. So it had to be extrenal. Has to have a ground to read on and there wasn't anything hooked to it. Pulled wiring and repaired about 6 spots total on the harness. Fixed a couple other problems too I didn't even know it was having.

Have them pull the wire loom off and CAREFULLY inspect each wire. The lmm that gave me problems had a bare spot on the wire about the size of a pen dot.

I've got a thread on here somewhere about it

 

[Sierra3500HD]

Never heard of a P0276.

Sorry mike P0762 is the code and the transmission shop has done countless amounts of hours on diagnosing tcm harness

 

[Mike L.]

Sorry mike P0762 is the code and the transmission shop has done countless amounts of hours on diagnosing tcm harness

I suspected that you crossed the numbers.
The code indicates that the shift valve is either stuck in the stroked position when it should be destroked or the Pressure Switch Manifold thinks it is because something caused it to ground.
The TCM gets its feedback from the manifold to let it know the valve either is stroked or destroked. A stroked valve will ground the little pressure switch on the manifold and let the TCM know the command was followed correctly.
I doubt very much that the valve is stuck as it is rare for that particular valve.
Bad PSM can cause this ( very common ) or a short in the wiring system.
Yes a bad solenoid can cause this also but that is rare as well.

 

[Sierra3500HD]

I suspected that you crossed the numbers.
The code indicates that the shift valve is either stuck in the stroked position when it should be destroked or the Pressure Switch Manifold thinks it is because something caused it to ground.
The TCM gets its feedback from the manifold to let it know the valve either is stroked or destroked. A stroked valve will ground the little pressure switch on the manifold and let the TCM know the command was followed correctly.
I doubt very much that the valve is stuck as it is rare for that particular valve.
Bad PSM can cause this ( very common ) or a short in the wiring system.
Yes a bad solenoid can cause this also but that is rare as well.

I got all that but the shop is still stuck on this issue with no result all wiring tcm transmission have been replaced and diagnosed.. Time to buy a new truck? Invisible problem that can't be resolved..