have an 07 denali.....so the wife mentioned a while back that she was driving and then all of a sudden the check engine light came on, service stabilitrak came on, parking assist off, and the little indicator bar under the gear icon disappeared. by the time she got home the lights went out and was back to normal. The check engine light came on once while i was driving but went away the next day. Today the same issue happened with the wife (note the common thread here ..) and the check engine light stayed on. This time she had to pull over because when she was at a stoplight and tried to start going again it would go above 20mph, kinda like it had a rev limiter. She pulled over turned it off, waited a couple of minutes and fired it back up with only the check engine light on, made it home just fine. So..pulled the codes and its a P1825 Transmission internal mode switch: value out of range. P0700 generic transmission fault code. Anyone with any insight as to what the P1825 means in english please let me know. I'm planning on taking it in to the gmc dealer tomorrow but im very good mechanically and dont care to get taken for $$$. If anyone has an assembly diagram or wiring diagram or anything that will help me find this internal mode switch I would really appreciate it. Help!