You are right on target actually, and part of the $700 that the dealership charged me one of the many times I was screwed over involved a new shifter selector lever, and a complete wiring harness swap. They tried every single electrical option possible because they did not want to admit they did something to the internals of the transmission. I did countless searches on this forum and other car forums that have the same transmission as ours and the only other occurances like mine were because of low fluid and the whole transmission was replaced in all the other sites. Our trans is actually shared with a ton of other vehicles. It is a GM 4L30E trans and has a 2 vavle pump inside of it and the valve body inside of the trans is terribly designed and was what first gave out due to low fluid and is very costly to service. I still have an extra mode selector switch (shifter lever) in the garage from Merlin at St Charles just in case this is a problem ever again.