In order for the plx m-500 to datalog, two inputs must first be connected. The two wires are said to accept 2 speed signals. A speed signal "measures the frequency of signal pulses", and a compatible speed input is defined as "an oscillating pulse which switches between a high and low voltage. A valid high voltage is 2-25V, and a valid low voltage is 0-0.8V. Does anyone have a clue what produces such signals on a TII ecu?

 

There's a road speed sensor in the speedo that sends exactly that type of signal to the PS, AAS and cruise control computers.