Hello- I'm new here and have an issue with my 1994 GMC C1500 5.7 'K' 4L60E transmission. It has went into 'limp home' mode. It's been a very good truck with virtually no issues to this point. Checked the ECM for codes- got DTC 12 stating system's functioning. Also got codes 66, 67, 81, 82. If I clear the codes the truck will run fine for about a mile, and it goes into 'limp home' mode again. The DTC lamp doesn't come on at that point. I'm getting 12.5v at the transmission fuse-key on, and key on engine running. I haven't checked anything at the transmission connector yet. Darn catalytic converter's right there in the way. I did, however, unplug it and didn't see any dirt or Dexron seepage. I have read on other forums of people just throwing shift solenoids and parts at these things with no resolve. I don't want to do that. I am hoping to get some constructive direction here to resolve this issue. I want nothing to do with these unscrupulous repair facilities that are out there these days, either. Thanks for your time and consideration.