Is the sender for the speedomoeter a simple linear 0-5V?

If so, does anyone by chance know at what speed it's officially "pinned"? obiously 0 mph = 0V. . .Xmph = 5V? (X="pinned")

I need to control a device based on speed, and thusly need to know what the signal is.

Thanks
ryan

 

voltage is 4.5-5 when stationary. 2-3 when driving but read by e.c.u.as a square wave. cheers Phil