7.3 ICP Wiring Issues

Marty · Jan 8, 2015

I was able to drive the truck around with the 2nd pcm for about two days without issue. I found a ground that has two in on one side and three out on the other that lays right up against the 5v signal. The grounds are for the 5v references elsewhere in the truck. I separated these wires because with the scope everywhere around that junction was extremely noisy. Basically the further away I got from it, the less sporadic the signal was, on either side. So I drove the truck around for a day with those two wires pulled out of the harness and no problem. So I replaced the ground wire and isolated them from the rest of the wires and then put everything back together.

So far so good.

mandkole · Jan 8, 2015

well done.. good sleuthing right there.

psduser1 · Jan 8, 2015

Marty said:
I was able to drive the truck around with the 2nd pcm for about two days without issue. I found a ground that has two in on one side and three out on the other that lays right up against the 5v signal. The grounds are for the 5v references elsewhere in the truck. I separated these wires because with the scope everywhere around that junction was extremely noisy. Basically the further away I got from it, the less sporadic the signal was, on either side. So I drove the truck around for a day with those two wires pulled out of the harness and no problem. So I replaced the ground wire and isolated them from the rest of the wires and then put everything back together.

So far so good.

These grounds are in the engine harness, if I understand correctly? Or the chassis harness between the pcm and the 42 pin connector?

psduser1 · Jan 8, 2015

Marty said:
I was able to drive the truck around with the 2nd pcm for about two days without issue. I found a ground that has two in on one side and three out on the other that lays right up against the 5v signal. The grounds are for the 5v references elsewhere in the truck. I separated these wires because with the scope everywhere around that junction was extremely noisy. Basically the further away I got from it, the less sporadic the signal was, on either side. So I drove the truck around for a day with those two wires pulled out of the harness and no problem. So I replaced the ground wire and isolated them from the rest of the wires and then put everything back together.

So far so good.

Just wonder if some thing like this could explain some of the issues seen in the excursions?