According to the AutoProm manual (here) the innermost switch must be in the outboard position. In the innermost position, 160bps / 10K resistor across AB is selected, which puts the 7747 ECM in ALDL mode (I presume) and forces a 1000rpm idle....
Bingo!
I've told Moates that and should maybe try again. But it's another internet rumor started before Moates, that has turned truth and we will be fighting it for years. 10K is not needed for most 160 baud ECMs.
1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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