Can a PCM cause all these problems?

[1994Woody]

I really dig my 94 Caprice LT1 wagon... although I think my co-workers don't understand my fetish with this car.
Anyway, it has a series of bizarre issues that I don't understand and I think the common thing that links them all together is the PCM. Please tell me if I'm wrong:

Change oil lamp won't reset. No, it's not the switch itself- I tried jumping the wires to the switch.

ABS lamp is on- but can't find ANYTHING wrong with ABS. Just put new rotors/bearings on front to resolve the only issue I could find.

No signal to A/C compressor relay under the hood. I have voltage and ground, but no trigger signal from PCM.

Speedometer reads WAY too fast. When indicating 30MPH, it's doing 35. Indicating 43MPH is really 50MPH.

Am I wrong to bundle up all my issues and blame one component? If I replace it, do I have to have some coding done? I'm really only well versed in vintage and late model British stuff- all these OBDI American cars' electrical management systems are quite foreign to me.


Thanks in advance for sharing your wisdom!

[1slow96]

It easily could have nothing whatsoever to do with any of these issues.

[1994Woody]

It could, I was just throwing out the idea to potentially avoid one of those "Oh geez, all those things combined usually mean the PCM is toast" kind of discussions later.