Steamfins

I have a 96 Corvette LT4 6SP and I'm having an issue where my speedo will randomly drop to zero or go to 200mph when I'm driving. I've replaced the VSS in the transmission but I'm still having the same issue.

I don't think it's a bad replacement VSS sensor because the symptoms haven't changed at all with the new unit.

Any insight into this would be appreciated.
---
steamfins

MatthewMiller

The signal from the VSS first goes to the PCM, and then on another circuit to the CCM, which then sends it to the speedo, radio input (for variable volume control), and active dampers if equipped. When it goes out, are you noticing any tendency for the engine to stall at idle, especially when rolling and you disengage the clutch? If so, then the PCM isn't seeing the signal. OTOH, if none of that is happening, then probably is a fault likely either at your CCM or between that and the gauge in the dash. Intermittent electric issues like in a C4 always bring to mind possibilities of a grounding problem. C4s are notorious for that.