What output from ECM causes TBI to fire on 1985 S-10 2.5L.?

I have checked virtually everything. Pour gas down TBI, starts fine. Red wire at injector reads 12 Volts constant. Replaced injector no luck. No reading at light blue ground side (no + or - or continuity to ground). Fluke meter shows no reading on TBI when cranking engine. Checked individual wire continuity from back of ECM on both red and blue TBI wires(red becomes black/pink) - good. Cannot get ECM to enter diagnotic mode (flashing engine light 1-2 sequence) with tester or grounding with a paper clip. Fuses good. Truck overall too good shape to get rid of. Tired of replace and pray with electrical problems