Quote Originally Posted by delcowizzid View Post
we dont veiw voltages but the resistance withen the netres chip that changes the voltage on the pins.TBI to pfi v8 actually looks like it needs a couple of mods with resisters to be factory correct. anyone care to measure the resistance of the pins above on a TBI memcal to see if it has the 7.5K between the 2 pins of the v8 memcal setup
I have made a series of measurements including TBI memcals and posted the results. TBI memcals show 7.5k between the two pins.
http://www.gearhead-efi.com/Fuel-Inj...ull=1#post3374

The images above are for specific chips in the memcal. Those chips are connected to numbered pins on the memcal. Understanding how the ecm uses voltage on pin 56 to determine fueling mode involves studying the ecm schematics and / or having access to GM documentation. It may be a distraction if the goal is simply to make your engine run well.

Here is some work done by Cliff Harris which shows the memcal pinouts which correspond to the specific chip in the pictures above. Cliff's work has been very beneficial to this hobby. Notice how pins 53, 56, and 56 work together to provide the desired voltage for fueling mode select.

http://www.misterpeachy.com/VettePics/MEMCAL-ECM.pdf