[Gmecm] VSS pulse to a 1227730

[Karl Walter]

Hello.  I have made an optical VSS by using a photo reflector looking at black marks I put in the speedometer, on the spinning magnet drum.  This goes to a circuit that generates 5v pulses.  Works great for my '7747 installation, but I want to do the same thing for a 1227730 ECU in a different car.  My question, what happens if I just put the 5 volt pulse to the yellow wire (pin b10 on the ECU)for the VSS?  The signal won't cross zero, so I'm guessing it will not work, but If someone has done this and it works, let me know before I go through the trouble of making a split supply ckt, or going to pin c6 and changing the mag/optical bit in the PROM.