anyone have info on serial data to clusters?

[95 V6 J body]

OK, this is not a simple question, and it's going to take someone who is really deep into knowing the computer systems on late model vehicles, but I figured I'd throw it out there.

Does anyone have info on the protocol for the GM serial data signal that is transmitted to the gauge clusters? Right off the bat, I'm particularly looking at mid 90's vehicles.

The info I'm looking for is how the signals for the warning lights and gauges break out of the PCM signal.

If anyone can help, or even point me in a direction for getting info, that would be great.

[bszopi]

Mid-90s, as in OBD-1 (90-93), OBD1.5 (94-95) or OBD-2 (96+)? I know on my car (94), the warning lights (for the most part) are not from the PCM, but from their own sources. I think the OBD2 may come from the PCM, so we'd have to have a better idea of what you are looking for. If your name has anything to do with the year, then I'd guess you are looking for 95, in which case it probably doesn't go through the PCM (for warning lights at least).

[95 V6 J body]

Well, to start with, I'm looking for the 95-98 J-body cars. The PRND321, most warning lights and the tach go through the serial data. The high beam, directionals, CEL, fuel gauge, voltage, and speed are the only ones that have a wire going to the cluster. My gut instinct is that most vehicles that use the 8192 baud serial signal that are from similar years, even if they cross the OBD lines, use the same signal. My reason for thinking this is that a 96-98 J-body is OBD 2, but the cluster will plug and play with a 95, which is OBD 1.5. It won't work the reverse, because the 96+ has the theftlock in the cluster, but it doesn't affect backwards compatibility. I'm actually interested in where I can obtain the info on what GM used for protocol with them (IE, signal map for serial data).