I have 97 Blazer with only 24,000 miles. A few weeks ago while driving in 0 deg weather down the highway it suddenly jumped up about 1000 rpms. When I stopped the key would not come out and found the transmission would only run in 3'rd gear and reverse. I was concerned about expensive transmission trouble. It had several codes to do with transmission P1860, P0758, P0753, P0740 AND p0785.
It has stalled on me before and the Ignition switch was replaced when in warranty. The good news is that people that have this problem say it is due to ignition switch. Also GM has a bulletin out regarding this but no recall. So I replaced the Ignition switch and the Checkengine light went out and the transmission worked fine and the key came out of the ignition without pushing the release with a screwdriver from under the column. GREAT.
Now the problem is that 4 weeks and 1200 miles later the same problem has come back with cold weather. I checked the switch and I am not getting power to the white wire that goes to the Transmission fuse #24. I made a fuse with wires and a couple connectors. I plugged it into a hot connector in the fuse box and into the bottom where the transmission fuse was. Well this makes the transmission shift fine and the release works so the key comes out of the switch. I will replace the switch again since it is under warranty but this must be a big issue for other owners out there. Let me know if anyone has experienced this issue or have more detail about it. I may be able to help If you have any questions about testing or replacing the switch. Also if anyone has detailed wiring diagrams I would like to get these to better understand the issue, Thanks..