1227165 V8 ECM MemCal Resistor Network

DO NOT USE – FOR REFERENCE ONLY

Here is a VERY rough draft of my initial research in determining what the 16-pin chip consists of on the 1227165 ECM MemCal from a 1988 IROC-Z, 5.7L Automatic car.  It has since changed and I also have attempted to mimic the resistor network on a bread board with nice results.  Most connections are right on and a few are slightly off from initial measurements.  I’ll try to get the newest draft up here soon.

The 14 pin is under work and received work from Craig Moates as well as taking my own measurements from my MemCal to determine if it’s possible to "rebuild" that chip as well.

Here is the latest draft.  This was made from the original draft, after using the bread board with commonly obtainable resistors from Radio Shack. The figures between the pins are as set up as raw measurements from the chip, then the raw measurements from the bread board.  As you can see, most are extremely close, however, there is one that is a bit too far off for my taste.  For example, the measurement between outputs 57 and 59 were measured at 25.6K, but using two common 51K resistors in parallel, I was able to get 25.5K ohms.  Very close.  But, the pins between NC and the 56 (No Connection) were measured at 12.47K on the chip, but managed to get 11.8K from the bread board.  This was done to solely concentrate on the other values from "used" outputs to be as close as possible and for overall simplicity and reproduction from commonly obtainable resistors.  We "could" use higher resistance (somehow getting to 7.4K or 7.5K ohms) on pin 13.  The charts below should demonstrate how close the "used" ports are to the raw measurements from the chip versus the bread board.   Check outputs such as 56 to 55 or 57; or outputs 56 to 59; or outputs 50 to 57, etc.

GM Resistor Network Resistance Tables Based: 1227165 ABYA Calibration (TPI)

All values in K Ohms

Raw measurements from chip (16-pin)

Raw measurements from experimental bread board using common resistors (16-pin)

The following chart is the raw measurements from the 14 pin chip and the chart is non-scalable.  I made the chart into an image due to the notes I made and figured that would be the easiest way to do it.  I didn’t resize it due to readability issues – anyway, it’s only a 16 color GIF which is only 12K in size so loading time shouldn’t be an issue.

(Click image for full size)

After looking at the chart, I started to notice some readings that were interesting. Not necessarily the values themselves, but the differences between the pins as noted above.  For example, looking at rows 1 and 2, from columns 10 to 14, I measured a narrow difference of 1.85K to 2.2K ohms.  Looking at rows 1 and 2 from columns 2 to 9 (before the red dividing line), I measured a difference of 2.2K ohms pretty solidly.  Almost to the point where you can say the difference in readings of pin 1 and 2 to all other pins is about 2.2K ohms. This may be a huge key in recreating the 14-pin chip resistor network (which is much harder than the 16-pin).

Here is a chart if the different year and Camaro models and their respective ECMs used: