transmission problem code

I have a 1996 Buick Skylark. 3.1L engine automatic transmission. I have a code coming on the check engine light. Its a 1870 code (Manufacture Control Transmission.) Will this mean it needs to be rebuilt. Or could be mean something all together different? I had the transmission rebuilt 3 years ago to the date. Same week of Thanksgiving. It had 44,000 miles on it then. It now has 87,000 miles on it. GM only gave a 12,000 or 12 month warrenty for it at that time. Fluid was change about 1 and a half ago. Is this going to be an on going problem?

1870 is slippage perceived by the pcm, many issues can cause this the most common being a problem with the tcc valve bore in the VB, but this must have a thorough scan with a trans function scanner to look at slippage/gear ratio errors and solenoid operation.

Ended up getting it rebuilt at a private shop. You were right about the tcc valve bore. Its funny that I had to go to a regular erson. GM did not want to do it. They said that if they would fix it, they would replace with another transmission for about $3000. They would not rebuild it. But they also said that in another 50,000 miles it would probaly happen again. Because the transmission they would put in it has no had the valve bore fixed in them. Not sure why GM would replace knowing something is bad.

That is poor dealership management, my shop, Cad/Olds, we did our own repairs/overhauls unlesss the price would exceed a GM exchange, just laziness and lack of training, look they lost a nice job making that decision.