Hey everyone!
I decided to check under the hood for any bad connections today since its warm outside. I started with the transmission connector and wire harness I found that the green wire was damaged, like it has been chewed up or something. Then I spliced it with a butt connector along with a tad of dielectric grease, and tested it with my multimeter to make sure it was good to go, and finally I wrapped a good portion of the repair area with electrical tape for added protection. After I reconnected the battery I drove around in the driveway testing each gear and they all worked fine, also I checked to make sure that I couldn't start the car in each gear, except for park and neutral, everything checked out fine! So I checked for codes and so far code 12 is all that comes up. I will check for codes later when I go to work. Here is a couple photos I took of the harness, and if look closely, the green wire is damaged. Lets hope this possibly explains all those codes I got!

Nice job finding that wire, I am confident that was your problem, thanks for letting us know what you found!

As for the code 12, with OBD before OBD II, if you get that while the car is not running when you test for codes, then that is totally normal, it is checking for a reference pulse that is only there when the car is running.

Some good news I have is that when I got to work early, I checked for codes, and only code 12 and 29 came up. Iam going to do some more investigating, hopefully I can get that code 29 tracked down.

I wish I had a manual for your make/model, then I could look at a diagram to see just what is being ran on that circuit, it could be up to 4 things, possibly injectors, not sure though.
I do know that the quad driver module is in the ECM, and either the ECM is bad, or there is a problem with something that circuit is running, which you want to be sure you find/fix it if there is, or else if you replace the ECM there will be a chance that new ECM with get damaged as well.
I wish I could help more.

I have the big thick factory service manual for the 91 Olds 88 Royale, and it mentions the 4th gear switch throughout the book along with the wiring diagrams. I did notice that a lot of that ribbed black plastic tubing that covers the wires has disintigrated and when I was repairing the wire earlier the stuff just crumbled when I touched it. So I am going to inspect that entire part of the harness since more wires could be damaged by rubbing on something. I appreciate your help! I will certainly keep you all posted. At least I got rid of the other 5 codes, and hopefully this one will be solved.

Here is the latest on those codes(27,28,29.). After I fixed the broken wire on the tcc connector, the code 29 was all the came up, until the next day when the other 2 codes showed up. Anyways I decided to just go and get another tcc connector / harness from the junk yard, I found a couple in excellent shape so I bought both. I removed the old connector and noticed that it had some kinked wires that also were exposed in places. I then spliced the new connector / harness in, and made sure that all five wires were making contact. Well I checked for codes after getting home from work yesterday, and the 3 codes were back! I said screw it, and I went and removed the original ECM, swapped out the M CAL chip and put it in the ECM I bought a month ago from the junkyardate and installed it. It works and everything but those god damn codes are back. I find it hard to believe that each gear switch is setting theses codes. What are your suggestions on what I should check next?

I am not 100% sure, but I believe the DTC'* are stored on the Mem-CAL chip.
Did you ever clear the codes before, or after putting the junkyard ECM in?
If not clear the codes, then drive it for a while, and see if the codes return.

Hows it going! Well I had some free time today to reset the ECM and I took a test drive on the interstate, around town and on the frontage road that leads to my subdivision. I used different gears for some of the areas such as overdrive on the interstate, D for around town and 1st and 2nd on the dirt road leading up to my neighborhood, and each gear seems to work just fine, so once I got home I checked for new codes and code 29 is all that came up. And to answer your question William E, I disconnected the battery yesterday before I swapped out ECM'* , to make sure nothing got fried in the process. I forgot to mention that I finally hit the 200000 mile mark a couple days ago! Anyways I am going to keep looking deeper into the wiring and test for any shorts or damaged wires. Another thing I noticed is that the SES light has not come back on like it did before whenever I was at a long stop light. I just don't want to fry my transmission with this possible wire issue, so I am hoping I can figure out whether the wiring is the issue or the dreaded 4th gear switch itself.

Good morning everyone.
After doing some more inspecting and testing of this dreaded wiring issue, I have found something rather interesting: On the round 5 pin connector that connects to the tranny, I did some testing with my digital multi-meter and found that when I have the key turned on to run, each of the pins registers around 12.23 volts, except for the tan wire which only registers 0.02 volts. According to the FSM all 5 pins should be around 12 volts! So I have been checking for codes when ever I get back from a drive and the 27, 28, and 29 codes keep showing up after I disconnect the battery to clear the codes. As I have been studying the FSM, it mentions that the brake switch is connected to this circuit. However I don't believe the transmission is the problem since the tan wire/ pin is not getting 12 volts like the other 4 pins, so the problem is either with the ECM, the brake switch or the wiring between each other. Does the brake switch seem like any area to test?

Good evening guys.
Well I have not been able to make much progress now that we have a foot and a half of snow outside and it being cold as well. Anyways I have gone a couple of weeks without clearing any codes just to see if any additional ones popped up. So on Saturday I went to check them and the whole bunch showed up along with 2 new ones: 22, 24, 27, 28, 29, 31, and 39. 22 for the TPS sensor circuit and 39 is for the torque converter clutch circuit. So I reset them again and now 27, 28, 29, and 31 are all thats there like before. And for several weeks now I have been noticing a really big drop in MPG'*. I have been very good at keeping more than half a tank of gas at all times and I always fill up before the needle gets to the half way point, also I have been putting in the middle grade gas for about a month now since its cheaper. As for the last 5 fill ups, only 3 have been around 19 to 20 MPG and for the other 2 its been like 10 MPG!!! in between the normal MPG'*. Of course its known that the winter gas usually results in a loss of 2 or 3 MPG'* so I don't know what to think about this.