[Gmecm] Shift light

[Robin Handley]

Anybody played with the shift light (pin A12) in a '727 or its equivalent in
a '749?

Going by the circuit diagram for a '727, ignition volts are supplied to the
non-ECM side of the shift light. My limited electrical knowledge tells me
that the ECM ground this pin when it wants the light to come on. So, when it
wants the light to be off, the pin should be at battery voltage. Is this
right? Same deal for the injector pins?

Could be my minimalist installation causing bypasses in logic (although
can't see why), but I see no voltage on the shift light pin, whether the RPM
is below the light on threshold or not. Am I missing something?

Robin