My 2000 has gotten the P0742 (TCC PWM solenoid stuck on) code for years. It's worse in hot weather. I'd cringe as the tranny slammed into higher gears on upshift (never downshift, as I recall). It was always a P0742 error code, never P1811.
You asked if the PCM "reprogrammed" itself. Normally, after I shut off the engine, and the engine/transmission cooled somewhat, the car was "good to go" until the next time a few days, weeks, or months later. The SES light would remain lit for the next 2 (or 3?) good (non-P0742-incurring) drive cycles. This usually meant the next 2 or 3 drives, with SES light lit, and car shifting normally.
I considered a shift kit, but wasn't sure it would help, because they were discussed mostly with regard to fixing the P1811 "long shift" problem, which my car didn't show. Last fall I finally sprung for a ZZ Performance transmission shift kit, after thinking about it for years. They recently upped the price from $30 to $40. Add $10 shipping and the total cost is $50. I was surprised by what the kit consists of: six nylon spacers, of which you (normally) use only four. I happened to have a whole drawer full of them left over from some basement project or other.
One double-sided page of instructions came with the kit. No pictures, no drawings, no diagrams. I searched around on the web, regarding the P0742 error code and shift kits, and found the following link very useful -- it has pictures that helped a lot. I just checked, and the post is still there. The guy is using a different shift kit (metallic spacers), but the kits are similar, and the general process is the same. The description and pictures of his progress, and the accumulator, assembled and disassembled, were just invaluable to me. In my opinion, the kit instructions should definitely have come with similar pictures -- no good reason why not, and it would be a great improvement.
Here is the link:
http://www.ls1tech.com/forums/ls4-pe...tch-movie.html
Despite the name of the link, I didn't find any movies, but the pictures were good, and very helpful.
The spacers modify the 1-2 shift and the 2-3 shift.
The job was a bit messy working with those accumulator pistons. You drain the fluid out of the accumulator at the start, but as I recall, it's recommended to fill the accumulator cylinders with fluid as you put it back together, so do it outside, on an absorbent surface, keep your mouth closed, and don't ever have your eyes in the way of the fluid.
As to results...so far, real good. I was a bit disgruntled about the kit (maybe you can tell), but I must say it is working well. The quicker shifting is a treat. It's not rough or annoying, just satisfying. Best of all, I think the P0742 episodes are rarer. One occurred last fall, but the slamming on upshift was much less evident. That was a good thing; hope it's permanent. I was going to wait to report on this, until this fall, after a summer's hot weather, including towing my boat, but maybe this info will be of help to you guys now.
BTW, I've used Seafoam TransTune the last two times I swapped out half my tranny fluid. As suggested, I used half the can beforehand, as a cleaner, and the second half with the new 7 qts of fluid. For what its worth, their website makes a big point that Transtune does not operate by swelling the seals in the transmission.