Glow Plug Circuit failure help...

[toobsluver]

I am currently having an issue with my excursion. Check engine light came on, checked and cleared the codes just to have the light come back on. Now it's fixing time. In the mean time as I do my research maybe someone can give me some insight to this problem or if someone has had this problem before let me know what worked for them. There is a lot of acronyms thrown around on these forums. For instance some one blamed the HPOP... ummm what's that? Anyways my 2000 X has about 125K on it, and it's only used on the weekends. I also use my super chips tuner set on high performance all the time. Inspection is up on my truck and the laws have changed here in NJ so I don't know what they are going to do. I still don't like the dummy light being on though and I wanna fix it. Luckily I have a Haynes superduty manual to help along the way. Here are the codes:

P0678 Cylinder 8 Glow Plug Circuit
P0676 Cylinder 6 Glow Plug Circuit
P0674 Cylinder 4 Glow Plug Circuit
P0672 Cylinder 2 Glow Plug Circuit

And that's it.

 

[toobsluver]

I'm finding out more, looks like I am going to be doing some electrical circuit testing and some visual inspections. From what I have read here are some options, GPCM (glow plug control module), loose or poor connections on glow plug wiring harness, under valve cover harness, and under valve cover retaining clips. The under valve cover conncector retaining kit PN through Ford is 2C3Z-14A163-AB. I'm going to eat breakfast then go out and check connections and ohms going to the glow plugs for issues. Any idea where I can get the Glow plug control module?

 

[JLDickmon]

my bet would be a UVC harness or one of the wires from the GPC

 

[toobsluver]

Yeah I just learned something new. All excursions have GPCM glow plug controller module. Other trucks had the GPR glow plug relay. Now I am doing Ohm testing outside the valve cover first. I'm getting no reading on the bad side (driver 2,4,6,8) gonna test the passenger side and see what I get.

 

[toobsluver]

The silver thing in the back is the GPCM ( glow plug control module ) Sorry for the poor quality, cell phone.

 

[superdub01]

i hope when you're saying you get no ohms you know that the more ohms (a measure of electrical resistance in a circuit) the worse the problem. any circuit consumers like a resistor, or a motor should have resistance, but in a perfect circuit there should be no resistance at all. Resistance can be caused by corrosion, damaged wires, failing components, etc. the only time you should worry about resistance is if it is too high, or if the meter does not give a reading at all indicating an open circuit. then to diagnose the open, you can perform voltage drop testing. hope this helps, if not give more details and hopefully you'll get her all fixed up. if you need it, i can give you details on testing resistance in a circuit, or voltage drop testing

 

[JLDickmon]

I wrote a thing on voltage drop testing last year..
lemme see if I can find it..
(it was supposed to get moved to the Wiki but never made it)...

here it is..
start with post #58