Well, I FINALLY figured out my code 15 Error and the source of the problem! After doing several checks with my VOM (Volt/Ohm meter) in different locations on the Gray/White stripe wire for the presence of 5 volts (From the ECM to the ECT Sensor plug.....No shorts, 5 volts always present (Key in on position, Engine off, ECT Plug disconnected)....Then I proceeded per instructions to check back the Light Green/Black stripe wire on the ECT Temp sensor plug for the stated voltage drops at different engine temps.....Bingo!!!.....Voltage drops were out of specified range!.....Problem was....... Poor grounding contact of the Black/Green stripe and Black/Blue stripe wires on the back of the intake manifold. My 94 4Dr Metro had 2 sets of ECM grounds that are grounded on the back of the intake manifold. 1 set of grounds is the Black/Green stripe and Black/Blue stripe .....The other set was 2, Black with yellow stripes on them. I removed both sets, cleaned them up real good with a wire brush, cleaned the mounting surface(s) on the back of the intake manifold also, tightened both ground bolts good (10mm).....It's been 3 days and over 150 miles of driving.......No CEL or code 15 coming on anymore....
.....Luckly, I have a good friend at the local boneyard who allowed me to pull a matching ECM from a donor car and check for a bad ECM.....Wasn't the problem after all!