The throttle position sensor was bringing up the SES light, so we checked it out and the little notch that clicks in and holds it in place was broken, thus the connector was loose or something. We took it to a pretty huge GM dealer nearby and they were able to help us get that fixed. That went away now
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We knew him personally so we asked if he could check things out, so he hooked up a connector to it. He said the PRNDL Switch keeps bringing up a DTC and also the EGR Valve and IAC Valve come up and go away, which he said can be an indicator of a problematic PRNDL switch. I told him what the guy at Master Transmission checked and he said that, while he doesn't specialize in transmissions, they concurred that he really didn't check anything. Just like you suggested, he said they have *got* (he was emphasizing that) to check out the pressure control solenoid and the other sensors involved.
I don't work on Saturday so we are going to finally investigate further. I'm going to buy that PRNDL switch (which seems to have multiple names, apparently) and we're going to switch them out just to get that out of the way and see what that helps. We're going to do some electrical tests of what we can and other diagnostic procedures that aren't too hard just so we can rule things out and say we did what we could. If it still isn't solved, i'm going to call around to two nearby shops that do Transmission work and see what they would charge to examine my transmission problem for me. If it all magically goes away (i'm doubting that, but you never know) then I will proclaim the good news
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