Since you have a lt1 in your 84, the engine code would be lt1.

As far as the the vehicle goes, use the vehicle that pcm came out of. My best guess.

 

Gave up in frustration and limped into mechanic to sort out the computer. Same shop that retuned my old LT1 conversion. (guess I need professional help)
But his code reader can't communicate with the computer either...

See my other post about the coil -- maybe it's a 96-97

Drove it long enough Saturday to get a check engine light. My previous drives (out a couple blocks -- still misses -- limp home) would not set a check engine light. When I had no luck with that code reader, I went back to jumper pins A-B. That also got no code, not even the code 12 that I should get with the engine shut off. Check engine light stays on steady. Jumper did cause the engine fan to come on, so I know it's connecting. And with the engine running, check engine light flashes like it's showing fuel/air properly, about 50% on/off time. Just no codes. And of course the check engine light is not on when I take it to the mechanic...

 

Only 93 lt1 cars can jumper the pins to flash codes. 94 & 95 pcm is obd 1 and must use an obd 1 scanner to read codes.

96 & 97 pcm is obd 2 and most any newer scanner should read the codes.

You might have a aldl wiring problem. I suggest going to the following site and downloading the 94 or95 service manual, depending on 12 or 16 pin aldl. It will have aldl wiring diagram.

Make sure your aldl has battery power & grounds at the proper location. And make sure data lines tp pcm are good. I'm assuming you have obd 1 pcm & wiring in your 84. www.mediafire.com/?40mfgeoe4ctti

You could also try the free scan program "scan9495" made for 93-95 lt1 f-bodies. Since you have an obd 1 f-body pcm & wiring in your car. It will read your codes, do running sensor scans.

You will need to download Microsoft dot net framework version 4.0 or newer to use scan9495 Get it at same site you get scan9495. Or go to microsoft site. Scan9495 is at www.mediafire.com/?0elo4c935uc5s

Download newest version in lt1 v8 folder.

You will need a cable to connect car's aldl to usb port of pc based computer. Get the 12 pin or 16 pin obd 1 cable, depending on which your car has.
OBD Diagnostics

Scan9495 was written by our member GaryDoug. So any questions on program can be directed to him via PM.

 

Just read your coil thread. If you indeed have a 96-97 obd 2 wiring harness running an 94-95 obd 1 pcm & systems, there could very well be some mis matches in the wiring to pcm & components.

You need to go to link for service manuals I posted in your code reader thread. You are going to have to compare your obd 2 wiring harness connections to an obd 1 wiring harness connection and see what's not right.

The manuals have full wiring diagrams. Also in driveability & emissions section will be a pcm connector chart which lists every pcm connector and all of their individual cavities. This chart will show you where every wire from pcm goes & what color wires are.

Combined with the wiring diagrams in electrical section, you should be able to figure wiring out.

 

The obd wiring harness might have some different pcm connections than obd 1 harness. Obd 2 harness also has more wiring connections than obd 1.

Most of the extra wires can be disregarded if they don't go to obd 1 needed pcm wiring cavities or components.

Make sure aldl wiring & instrument cluster wiring is correct for obd 1 use.

And keep in mind that changes were made between 94 , 95 & 96-97 that can effect engine & transmission function. If running an automatic trans, pay attention to trans wiring harness as GM made year to year changes to trans & it's electrical components.