1999 7.4 Low sensor voltage P1122 P0122

[rdomeck]

It's fixed.... I pulled the harness and found the 5V reference wire for the EGR circuit was shorting to ground. That circuit is also the 5V for a couple of other sensors. I suspect that they are al fed from the same point inside the ECM making every sensor not do its job.

It is very small, but you should be able to see it in the attached pictures. It took about an hour and a half to pull the harness. Spent about 5 hours on the harness and another hour to reinstall. You can see the grey wire has been rubbed through. This wire goes from the ECM to 4 sensors and also in to the fuse block I believe.

What a bear, but at least it is fixed. Except now the fuel gauge doesn't;t work. I might have not plugged something in. Will check when it is light out!

Thanks for the help, nt time to tune this thing.

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[Schurkey]

Well, THAT made my day. Thank you.

I've been pissing and moaning about having to replace the starter relay-to-starter "S" terminal purple wire in my '97, and I didn't have to remove the harness, or strip the entire thing. I just had to strip a ~6" section, find the purple wire, cut it, and then attach a fresh wire from that point to the starter.

In other words, you just did a hundred times more work than I did, and I been feelin' sorry for myself.

 

[454cid]

Wow the whole harness!

 

[andy396]

Talk about finding a needle in a hay stack! I’m impressed!

 

[Christian Steffen]

Wow, what a pain. Glad you got it!

 

[rdomeck]

I'm glad a got it too. I missed one plug in at the firewall on the left side keeping the fuel gauge from working. Not bad for all that work. I guess I had a few more hours in this. Maybe 10 hours total.

Now I can start to get the rest of the work done to this.

Drove it a hundred miles today and had no issues

 

[Christian Steffen]

Hell yeah, good to hear.