Hi all,

I just purchased my 2004 F-250 6.0 about a month ago. Replaced oil cooler, caught up on services, etc and the truck has been pretty good. However, yesterday morning an issue developed. Temp got down into the 30’s the night before and was 46 when I came out to start it up, and nothing. After some cranking white smoke began pouring from exhaust, and after more cranking the truck finally fired up, smoke cleared (except for a little haze which later cleared) and ran fine. At this point I was pretty shook up, the truck had always started well but we had been in the 60’s/70’s up until then. I had no CEL, but scanned and found P0683 GPCM comm. fault, and P0671,3,4,5,7 and 8. Next start was 5 hours later, truck was pretty much cold. But temp had warmed up into the 50’s. Truck started right up for the rest of the day. This morning, again in the 30’s overnight, 41deg when I came out, after about 5 seconds of cranking, sounding like it wanted to go but not going, a big cloud of smoke comes from the tailpipe and she comes to life, runs and drives beautifully with no smoke. So, it seems that it only has a hard time starting on cold mornings, first start of the day. Is it safe to say it’s a glow plug issue? I have ordered a new module since I have a module code and so many glow plug codes. Really hoping it does the trick. Other thoughts?

Thanks in advance.

 

Sounds to me like the gpcm is gone. Did they all go at same time? or have you had codes over time and it just got bad? Lot of variables.

 

The GPCM code has been there since I bought the truck. It always seemed to start fine and never turned on CEL, so I didn’t bother looking at it. When reset it would always immediately come back as soon as I turned key. The individual glow plug codes only came up after the first episode yesterday morning, so I assume there is a larger problem here than just a bad set of glow plugs. I do find it strange that there is no code for 2 or 6. Maybe the gpcm is still working on those two circuits somehow?

 

There are some threads in here on how to test gpcm and glow plugs. It's a little bit of work to test plugs them self. If it was me and was thinking and doing all that work I would just replace glow plugs and there harnesses instead of testing all. You will probably break the harness plugs while removing anyway. Could just test or replace gpcm and go from there.

 

Some good info from DTR (start at about time 13:50 for checking resistance of plugs and harness):

 

Also:

6.0L Power Stroke Glow Plug System Troubleshooting Guide

 

Where did you order the parts?

 

RockAuto, OEM

 

I got a buzz going or I'd read that link, Mark. I have these same issues/symptoms, you may recall, although not the no-start yet. So, I'll just blubber ignorantly instead (yeah, yeah, I know)...Banjo, I'd check in with your GA FTE chapter here and see if one of our friends are in your area. Some of the guys here would actually climb off their...motorcycle...to come swap in their GPCM with yours to see if that solves the problem before I'd even give those plugs a side-eye. Pretty easy swap.

 

I have a new module on the way, should come in this weekend so we will find out soon. I will test resistance on the plugs too while I’m in there. Until then, gonna see if the block heater will help. If not, it still starts. It just isn’t happy about it whatsoever. But we’ll get by. Lol

 

Alright, the module finally showed up. I decided to test resistance on plugs before i put it in, and found some strange outliers. Here is what I have:

Cyl 1 - 11.0 ohms - WAY out of spec
Cyl 2 - 19.0 ohms - Again, WAY out.
Cyl 3 - .4 ohms - .1 below spec minimum, don’t think this is anything to worry about???
Cyl 4 - .5 ohms - Good
Cyl 5 - 1.2 ohms - Good
Cyl 6 - 1.6 ohms - Good
Cyl 7 - .5-.6 ohms - Multimeter couldn’t decide. Good
Cyl 8 - 1.1 ohms - Good

So it seems that all but 1 and 2 are within spec. It’s odd that 1 and 2 are at the very end of each GP harness, maybe they are not fully connected?

How does this harness work? Do I just push the connector onto glow plug?

I spoke with previous owner, all glow plugs and both harnesses were replaced last year, 12k miles ago. I find it hard to believe that they have failed.

With all of this said, is it ok to plug in the new module having such high resistance? The last thing I need is to fry this module.

Thanks

 

Bye doing the test, you proved you eather have 2 bad plugs. You can plug gpcm in and it won't change the outcome of the test you did on the harness and plugs. 2 plugs are Bad the way I see it.
Those 2 Could be loose, but doubtful.

 

Alright, I put the new module in and sent it, cleared codes and they’re back according to my edge monitor. Will take a better look with Forscan later. But I assume I’m gonna have to go ahead and buy glow plugs and harnesses, do I need to go OEM on either? Where can I find best price? Also, how do I know which ones I need? Door sticker on my truck says 03/04. ICP on valve cover so I assume this would be a late 04?

 

Be sure to get the shorter glow plugs.

 

The harness will get wrecked during removal. There are some special tools to help pull the harness off the plugs. Some people find it easiest to remove the inner fender for access. When we did ours on a Sunday, we could only find a harness from oreilly. Plugged it in, still had codes, seems the connector wasn’t deep enough to reach the contacts on the other harness.
Had to wait till the next day, OEM harness installed and all has been good since then.