My 2007 Super duty 6.0L threw a code with said that #8 glow plug is faulty. So I did a search on forum and read up on how to replace it.

I managed to replace the glow plug by removing the fender inner wall to gain access and cleared the code but the same code came back again right away.

The wiring harness doesn't seem to be broken or damage at all but is there a way to test the wiring harness? Would pulling harness off #8 then using voltage meter and turn ign key will work? Should it give me 12 volt?

I am not loaded and always turn to find way to save money on repairs whenever possible

Could it be any other reason it would throw that code?

I don't think it the glow module because truck still starts fine with the error code.

and also

This is my first Diesel truck owned ( yes I am aware about the 6.0L and wish I did research before buying a diesel truck but it went for cheap)

Am I doing any serious damage to it running on only 7 glow plugs? I am not out driving all over with it just like moving it around on my driveway to work on it?

I read on forums that folks are running their truck on only 7 or even 6 working glow plugs because they didn't want work on it during winter season and want to wait until Spring time to fix it .

Thank you

Bill

 

You will just have a rough start. Best way is to ohm it out from the gpc plug. But you can also check for voltage at the plug right after you turn the key on with a cool engine.

 

Ohm from the 4 pin buss bar to battery ground, with the engine off.

 

What ohm should I be getting?

Where the bus bar located at? Do I just follow the glow plug harness to the bus bar then unplug the bus and measure the ohm right?

Any images that have a connector with number 4 pin available?


Thank you

Bill

 

Should be under 5 ohms. Follow the harness from the glowplugs to were it plugs in to the engine hanrness

 

I posted something some time ago about the testing.
Here is a link to that info.
https://www.ford-trucks.com/forums/1...ce-manual.html


Sean

 

Got a bit more info for anyone that is looking.
Here are the two connectors (Green & Black) on the GPCM and
the two that the harness on each side plugs into.


Sean

 

Thank you for the information!!

It will help me out when I troubleshoot my truck tonight.

Bill

 

I think I found the #8 connector but I can't seem to get it unplugged so I could test the ohm on it.

Look like there a red slider bar so I pushed it as far I could outward but still refuse to come unplug.

In the photo below, is this the right connector and is there a trick to unplugging it?


I located it near the firewall driver side, next to a turbo air intake.









Thank you

Bill

 

By looking at the other connector schematic, maybe I should test ohm from the GPCM connector instead?

The GPCM connector look easier to reach than the one near the firewall


Bill

 

Push the red tab towards the ficm, the push down the black tab, pull it apart

 

I have had the p0678 code which is #8 glow plug. This is also a common code for the GPCM. If the temperature is over 70F the glow plugs don't even come on so this time of yr might not be the best to know how things will go in winter. I replaced both the #8 glow plug and the GPCM and the code went away. GPCM is about $100

 

I went ahead and measured from the GPCM connector instead since it was easier to get to.

On the black connector after unplugging it from GPCM, on cylinders #2 #4 #6 #8 I get a reading of .6 ohms

I did not unplug the green connector or measured the odd number cylinders.


Does it mean the wiring and glowplugs are fine then? So it most likely the GPCM then?


Bill

 

Can you point me to a place to get GPCM for about 100? I tried googling but some online store want almost 200 for one.


Bill

 

Here is one for $ 121.46 and it's a Ford part.
Diesel Glow Plug Controller for 2006 Ford F-350 Super Duty|YC3Z-12B533-AA

Sean