[Schnabel]

First of all, since I am new, I should introduce myself. I have been lurking for a while, but just registered. You guys have a great site!

My truck is a 2006 regular cab 4x4 with the 6 speed Allison. About 3 weeks ago, my tranny would erratically go into limp home mode, always on a cold start. I got various codes, mostly of solenoids stuck open or closed and the temperature gauge. So yesterday I dropped the pan and replaced the pressure switch. I filled it back up with dexron, and fired her up. After 5-10 seconds and still in park, the check engine light came on and the code was p0751. So I let it run for a couple minutes to cycle the new fluid through a little and then cleared the code. The same thing happened when I started it up again. P0751 (shift solenoid A curcuit perf/ stuck off).

I'm at a loss here because before it was throwing many different codes and now it just throws the one. Is this caused by the fluid change? Like a lack of new fluid on the new pressure switch? Any ideas? Should I let it run for a while to see if it works it out? Or should I replace something?

Thanks for any help y'all can give me! I appreciate it!
-James

 

[Mike L.]

Check for disconnected wire at the solenoids.

 

[Schnabel]

I checked wires when I did the PSM swap. They all seem okay and they are plugged in. I am curious if this problem is caused by a loss of prime? And if so, how is that fixed? I've read every thread I could find on this site and others, and most lead to
a) NSBU switch (but those I think are usually the external NSBUs?)
b) Ignition switch replacement to get sufficient power to the TCM
c) Unplugged wires

I had one of the codes before that was p0843, which I have read before that p0751 can sometimes be related to that, but I'm not really sure how...

I should also add that the truck has 448,500 miles on it, all stock.