With a 94 ECM there is a wire that runs from ECM to A/C. Is this simply a on/off for the a/c compressor clutch? Where is the ecm getting a signal from the hvac inside?
The ECM likely knows when the A/C is turned on; for one thing it's going to increase the idle air to maintain idle speed compensating for the load of the compressor.
The service manual wiring diagrams would tell that story.
What is the VSS used for on a manual transmission truck; is it just speed?
On my '88, the VSS is first interpreted by the instrument cluster. The cluster takes the VSS pulses, and turns it into multiple signals for the speedo-odometer, the cruise control, the ABS, and then sends speed info to the ECM.
I had intermittent problems with the speedo going to 0, the odometer quit working, the ABS quit working, and the cruise control would drop out. I'd get a MIL light on the dash. Sometimes, I could slap the instrument cluster, and everything would work normal again...for awhile. Other times, I'd drive 100 miles or more before it came back to life.
Eventually got a new cluster from the Treasure Yard, and everything was good for a dozen years. Now my Odometer doesn't work. Haven't fixed it yet.
I don't know how your '94 is set up. Again, look at the service manual.
Does the cruise control on a 94’ receive or send any information to the ecm? It looks to be a stand alone
On many/most GM vehicles, the ECM knows when cruise is engaged--the ECM uses that signal to modify the transmission commands and perhaps other functions (Throttle-by-wire, for example.) I think the general idea is to maintain high gear/TCC a touch longer when cruise is engaged, compared to not using cruise. Keeps the trans from "downshifting" and disturbing the passengers as much. Also gains 0.0000000002 mpg.
I know this is a factor on my '92 Lumina. I think it's a factor on my '88 K1500, but the only thing the computer controls on the '88 is the TCC.
How this affects a vehicle with a manual trans is beyond my experience.
I’m looking at a Port injection intake using Vortec harness/sensors and 0411 pcm but want to have everything fully functioning. I’m trying to narrow down any issues I may have
I can't help you with that. Sorry.
