Write Up: Installing a 1997 PCM into a 1996

Obvious disclaimer: I am not responsible for anything if you dick this up.

WARNING: I experienced some transmission issues a few months after doing this swap. Who knows if they are related. It could have something to do with importing trans files from other tunes instead of entering them manually. YOU HAVE BEEN WARNED.

Now, first off you might be asking why someone would want to do this. There are a few different reasons such as the ability to use HPT instead of DHP, more tables available for tuning, etc. It is also a fairly cheap and easy swap as long as you already have DHP and a basic socket set.

Tools/Materials:

Basic metric socket set (6mm - 15mm).
Phillips head screwdriver (optional, you can use the sockets instead).
Flat head screwdriver (optional, can make disconnecting the trunk release lock connector easier).
1997 Riviera PCM (other ones may work, but this is what I used).
DHP downloaded, installed, and configured. It might also be a good idea to be familiar with how to use the program.
TinyTuner downloaded, installed, and configured.
1997 Riviera .bin file (in case DHP gives you issues reading the new PCM file. The one I used will be linked below).
The ability to read and check for wires.

How To Remove Your Old PCM/Install Your New One.

1: Disconnect the negative terminal on the battery under the rear seat. You may experience PCM damage if you don't.
2: Unscrew all of the bolts holding the glove box on. There are about 5 little ones (8mm?) and one big one (10mm?).
3: Unscrew all of the bolts holding the black hush panel on. There are about 5 little ones (8mm?).
4: Open the glove box and gently pull it out. It will take some finangling but it should come out with minimal hassle. IMPORTANT: There is a connector on the bottom left that goes to the trunk lock switch. The wires do not have much give so disconnect them as soon as possible.
5: Pull down on the hush panel. You do not need to remove it, and can just leave it sitting on the floor. There are a pair of wires that go to a light on it so be careful.
6: There are 2 long rectangular connectors that go to the PCM, a blue one and a clear one. each of these are held on with 1 bolt (7mm?). Make sure your battery is disconnected before removing them.
7: There are 2 plastic clips that hold the PCM in place, one on the left and one on the right. I was able to just move them by hand, but you may need a flathead to do so. The PCM should pull right out after being released from these tabs.
8: IMPORTANT: Verify pin 35 on the clear harness has a red wire. If it does not you will need to do some wiring and are on your own.
9: Screw in the 2 connectors to the new PCM. I did not button up everything yet for fear of something not working.

How to configure your new PCM:

1: Plug in your computer, turn the key to accessory, and start up DHP.
2: Read the .bin file from the new PCM.
3: Save the file in a known place under a known name and open it with TinyTuner.
4: In TinyTuner, under Transmission > Gear Ratio > Transmission Type change the value from 2 to 3. This changes the PCM from controlling a 4T65E to a 4T60E. Value 0 is for a manual, 1 is for a 4T80E.
5: Save the changes and then save the file, close TinyTuner, and open the file in DHP.
6: Transfer any tuning changes over to the new file. IE: MAF, Timing, Shift Points, etc.
7: Flash the .bin to the new PCM doing a FULL WRITE.
8: Once the flash is complete and you have waited the 20 seconds with the key off, start the car and go for a test drive. Mine fired right up and shifted perfectly. Just take it easy because you may have some tuning to do to get everything back to where you wanted it to be.

Possible issues:

VATS: Some people may need to disable VATS in the .bin file. I didn't, but it could be the cause of a no start for someone else.
Gear Ratios: Our cars SHOULD have the same gear ratios throughout 96-99, but it can't hurt to double check them.
CASE Learn: You may need to do a case learn, a common issue when switching to a new PCM. DHP can do this and so can a GM dealer.
SES Lights: There may be some SES lights due to the fact that the device the PCM is trying to control simply aren't there. Delete them as needed (I'm still working on this part).

My '97 .bin (uses modified shift points, SES codes, torque management, 180* thermostat, and MAF table. Change as needed):
https://www.dropbox.com/s/jnbmuwu19jek9oh/usethisone.bin?dl=0

Update: I matched all of the SES codes, enabled the ones that the '96 had enabled and the same thing for the ones that needed disabled. Any extra codes I disabled. On first start after flashing a tune I get an SES light but it comes up with no codes found. When I clear it it doesn't come back until I flash another tune. Ideas?