1997 GMC W4 EGR Code P1406

I have watched the youtube video on code code P1406. I have the same code on a 5.7L V8 GMC W4. I have followed the testing procedures listed on the video and was able to manually energize the solenoid. The 2 outside wires, 1 has around 12 volts (Brown and Red), and the other one around 10.95 The issue I am noticing is that my 3 middle wires all have around 5 volts. Not showing 0 for a ground wire, so not sure how to proceed. I have attached the wiring diagram below.

Also showing a P0102 code, not sure if its somewhat related.

Thanks in advanced for the suggestions.

You have an open in the White wire (ground). Repair open and confirm G/R (signal) wire integrity by jumping G/Y(5V ref) wire to G/R (signal) wire and on scan tool "EGR position" PID should change. Alternatively if you ground the Green wire (egr solenoid control), the G/R (signal) should change.

Thank you very much. I will look for the open and report results.

I really appreciate it.

Harry

The ground is shared with the MAP sensor, IAT and Trans temp sensor. If those temp sensors aren't showing -40* then it's somewhere between there. It doesn't have to be open it can be very high resistance in the wire or splice. Look for water intrusion maybe.

Well, this has taken an interesting turn. I checked continuity from the EGR pin to the negative battery post and nothing. I did the same thing with the map sensor and I got continuity to the negative battery cable. I am in the process of looking at the harness, and had to take a minute to take some pictures to show what I have found. See attached pictures. This is in my opinion a total mess.

Still trying to find the wire as it seems to have been re-routed a different way. Will be back with an update later.

And finally, the mother load!

See attached.

Awesome! I would have run a new line cause i'm lazy.

Thanks for all the help, I really appreciate it. Of course things get a little more exciting. I found 5 white and blue wires joined into a single line. They were wrapped with duct tape which looks pretty bad. Further down there are 5 white and blue crimped with another 3 white and blue lines. I have no clue what they did to this truck.

Some more pics attached.

Both codes P1406 and P0121 are and gone and check engine light is off after repairing the open in the ground wire.

Thanks for your help and guidance on this repair.

Now to tackle the rest of the wires.

Both codes P1406 and P0121 are and gone and check engine light is off after repairing the open in the ground wire.

Thanks for your help and guidance on this repair.

Now to tackle the rest of the wires.

So the P1406 code is back. Wiring and EGR tests show it is working properly after repairs. Not sure where to look now?

Thanks in advance.