Anyone using/logging VSS successfully on car with cruise control?
I hooked up the VSS on my '97 and the result was not quite what I had expected. Initially, I had the VSS, OBD2, and cruise control module all hooked up in parallel (basically just tapped into 1M GRN-RED). The OBD2 and cruise control module behave as per usual (signal seems stable, cruise is steady when engaged), but the MS3 signal however has frequent spikes in the signal where the calculated speed jumps up substantially for one event.
I tried a few different things to isolate/eliminate the noise:
At first suspecting that I was getting a weak pullup voltage for the signal, I disconnected the OBD and went to attach a 5v pullup for the MS3. I discovered that the MS3pro was already configured with a clean pullup on the circuit I was using anyhow (oops!), but the result was still unchanged. So then I disconnected the cruise control module (with OBD2 already disconnected) so that only the MS3 was hooked up to the VSS. Now I get a clean signal that matches the calibration numbers as it should.
Next I reconnect the OBD2, so that the MS3 and OBD2 are both hooked up. Signal is still clean and good. Hook up the cruise control module again and the noise is back. So the cruise control module is definitely the cause of the signal noise.
Now, how to remedy the situation? My first thought was to use the MS3's VSS output to drive the cruise control. This kept the VSS signal clean, but the cruise control surged something terrible because of the lag time between input-calculation-output on the MS3. My next idea was to use the RSW terminal on the instrument cluster but to isolate it from the OBD2+CCmodule by cutting the trace and soldering a diode inline on the instrument cluster. I successfully modified the instrument cluster, hooked it all up, and... still getting noise on the MS3 VSS.
So, anyone got any ideas? How/why does the cruise control module create noise on the circuit? Any other ideas on how I can clean up the signal for the MS3 without sacrificing the cruise control?
* I've attached a log file that shows the VSS signal while "traveling" at about 34-35 mph. It starts with the cruise module disconnected and then again with it re-connected. The car was up in the air on jack stands, so you may notice that the load values are very low, but really it's just the VSS signal that I'm curious about.