k4ben

Thanks- Spent some time examining the harness for water intrusion, nothing so far and no obvious damage. It's older, only pins 2,4,5 & 16 to look at. I'll look at ECM power & grounds next.

I have a 2006 GMC Sierra 2WD 4.3L with electrical issues. A scan tool will not communicate with the ECM. I have a single line oscilloscope with which I see all the modules except ABS talking to the ECM. I have discovered that terminals 4 & 5 of the DLC have resistance. I have gone to the trouble of removing the dash in order to check the ground termination points. I cleaned them and re-attached the grounds. There was no difference with the readings, both had the original values, (4 ohms and 29 ohms). I don't see any damage to the wiring harness but I have noticed a water leak that seems to be near the pillar/windshield on the driver side. It does not seem that the water penetrated the harness. How should I proceed?