Check out this thread for background...
https://ls1tech.com/forums/showthread.php?t=331833

Sit back and relax, this will take awhile......

I went to the stealership today to get my Tahoe diagnosed for electrical problems that might be causing my 2nd gear solenoid not to operate. I installed a brand new tranny less than a week ago and 2nd gear is gone, same as the old tranny. My guess is a computer signal is burning up the 2nd gear solenoid because it worked (mild slipping) for 2 days before 2nd gear went completely away. The stealership told me that they could not diagnose my truck because of all the after market goodies on it even though I told them about the S/C two days prior, when I made my appointment. So now I’m back to the forum for help. I have no 2nd gear and I don’t know why. The solenoids are brand new and the new tranny is doing the same as the old tranny. The solenoid might be burnt up at this point but if I replace it, will it last 2 days and be burnt up again? Something electronic is screwing up my tranny and I can’t get any answers. Any suggestions? Should I replace the solenoid and hope for the best? There are no tuners in my area. I have one guy who works about 2 hours away who said he can try to help but if it’s not something in the tune then I wasted my time and $$. What else could be sending bad signals to the tranny? I have checked my throttle position sensor and MAF, both work fine. Yes, the tranny fluid is full.

 

Could Be Pcm Could Be Ground Problem Could Be The Wireing Harness In The Trans From The Out Side Plug To The Solenoids.could Be A Ground Problem In The Pcm.

 

Quick Thanks to Joe at JAG PERFORMANCE for talking on the phone with me and giving me some ideas. I'll let you know what happens.....

 

Joes a great guy I got my shift kit from them, whenever I have a tranny question I call him and he points me in the right direction. Whenever I blow this one I know whos going to be building me one.

Concerning your problem are there any se lights, do you have an aftermarket converter? Is it only second gear that youve lost or is it 2 and 3, do you have any scanning software.

 

just saw you have a 2200 stall, I would get an updated tune with adjusted voltages for the tcc and shift. I had a problem where shift voltages where off and it caused alot of slippage making it set 2-3 shift silenoid performance and I would loose first and fourth. this was before I had hp tuners now I got it fixed,

since this has happened before it might not be a mechanical problem. I would look into the tuning side first, then wiring then mechanical.
who made this tranny, shift kit?

 

I have no scanning software of my own. I do have an aftermarket stall 2200. No SES codes other than the "solenoid A circuit stuck on" that I got a week ago. (and an injector circuit open) I cleared all codes (at a shop) a few days ago and they have not reappeared. I was told to scan and see if the gear is being "Commanded" but I don't know how to do that. If I take this thing to a Transmission shop and not the dealer or general mechanic, would they have specific equipment to test the electronics of the tranny?

 

Most tranny shops wont have a clue and dont have the software to do that, did you tell Joe about the code? If you could get hold of some tuning software like edit or hp I think you could solve the problem, maybe someone on this forum is in your area. i really think the problem is in your tune I would contact westers

 

I have been in contact with them. Lyndon, the tuner at Westers, asked me to scan and see if the "Gears are being commanded" I don't know how to do that or what it means exactly. I'm trying to get them to send me a new tune in a new PCM and see what happens. But at this point the solenoid may be fried and a new tune may not solve the problem, but at least I would be able to tell if the tune is the issue. I might just call nelson and have them send me PCM and see if it fixes it.

 

Truck threw a code at me but I don't have a scanner to read it with. Shortly after, within minutes, I lost overdrive. I have an appointment tomorrow morning at a tranny shop that "specializes in late model electronic transmissions" Hopefully I can limp my truck there with 1st and 3rd, guess the 2/4 band finally crapped out....stay tuned.