I have been having issues starting in South Texas cold weather. Lows in the 30's or 40's. It is better if I cycle the key several times. FICM voltage is 49, running Ed's Atlas 40. IPR and ICP monitoring shows good oil pressure control.

In my research, I've found that most people don't suspect GP's going bad, but I've been suspecting issues for a couple of years, but last January, I was able to get it started(with difficulty) in 10 degree weather in Colorado one day. Rest of the trip was in a heated garage. This year it is worse by a lot. So far only a few days in the mid 40's and starts ok, but not normal and with white smoke. Two days in low 30's it was a struggle to start even cycling the keys. One of those mornings I was beginning to doubt it would start at all. Those two coldest days I had trouble in the afternoon as well, but the truck had sat for 4-5 hours.

Today I tested GPs from the harness. I'm not all that handy with the tools and I don't like working on vehicles, but I have learned that I can save a lot of money and a lot of hassle, as well as the thought of being taken advantage of if I don't do a minimum of due diligence. Here is the result from my ohm check.


Green connector
pin 1/GP5 - open
pin 2/GP7 - 107 ohms
pin 6/GP1 - 66 ohms
pin 7/GP3 - open

Black connector
pin 1/GP6 - 43 ohms
pin 2/GP8 - 0 ohms
pin 6/GP2 - 65 ohms
pin 7/GP4 - 0 ohms

From this, I wonder if I even have any GPs that are in good working order. The two 0's are 0.0-0.1 ohms. Two show not continuity at all, and the other 4 have real high values ranging from 43-107. I feel like I'm getting some value from cycling the key, but these values are not normal.

I'm considering changing all of them, including the harnesses, and possibly the GPCM. What does this result look like to you all? Is it valid to diagnose GPs through the wiring harness? Would you suggest changing plugs and harness or just plugs first. I've priced plugs, but not harness. I know the GPCM is $125ish. Hoping for some feedback.

 

Plugs are $11-17 each and the harness is $67-76 per side, Ford dealer. Easy job, #7 sucks. Bad plugs will give P0671-P0678 codes.

The harness is brittle, replace it. Cycling the key is bad, turn the key, wait to start light goes out, start the truck. The plugs will continue to heat for up to 120 seconds and that extra cycling can and probably did kill them. If the tip burns off and drops into the cylinder... your buying a motor.

I expect them to go bad, so should you.

 

To add, only use Motorcraft plugs part #

4C3Z12A342AA

 

What is the criteria used to throw a glow plug code?

 

What year?

 

Mine's a 2006. I don't want to hijack the thread. Actually assumed the criteria was standard across the 6L.

​​​​​​​Was hoping the criteria may help the OP in his troubleshooting.

 

I have an early build '04 and on ScanGaugeII I don't have any codes. I may check for codes with SCT tuner.

 

I checked DTCs with the SCT tuner. Codes for 1, 2, 3, 5, 6, & 7. So only 4 & 8 are working. I guess I'll change them all.

 

For the added 20 bucks it's not worth not changing them all. Alot of times once one goes they start dropping off. The biggest thing is the chance of breaking the harness to change just one. I'm sure you know the price of a harness.
So definitely do them all and it's done for another 12 years.

 

Big lesson... scan gauge is not good at code reading. Program the x-gauge for DTC and it will display a good number for the count of codes it has stored, but not read them well. Then use the tuner, Torque Pro, Forscan, IDS, AE, anything but Scan Gauge to get them.

 

Watson, lesson learned about ScanGuage as a code reader. I won't make that mistake again.

How much should I pay labor to have all 8 plugs and both harnesses replaced?

Where is the best place to purchase the harnesses? I see some on Amazon. Ford OEM's are about $55/each, but I'm not sure if they are the right ones for my truck. Early '04 build date, but it doesn't have the solid rail like the '03's. Are there multiple variations of the post '03 harnesses? The OEM product description on Amazon says it fits '05-'06. Other aftermarket harnesses say '04-'10. I guess they were still putting these 6.0's in the vans till '10.

 

I just did the same job about two weeks ago. I used the Ford dealer for the parts, just give them the VIN. They charged me $16 a plug and $67 for the right and $76 for the left... mine is early 04, just like yours.

It took me less than 1 hour per side. Unsnap the harness, yank the connectors off by hand, change the plugs, plug in the new harness and go. Passenger side requires a little more effort, remove the wheel well liner to access that side. It's not a hard job, go slow, account for your tools, take a picture if needed to remember the order.

Minimal tools required really. I'd expect a shop to charge 3 hours.

 

I wouldn't normally tackle this myself, but just bought a house and doubled my payment, so I'm watching pennies. I will do some more research and possibly tackle this after my parts come in.

Do you have the part numbers for the harnesses?

I suspect I may have to drive my daughter's car one or two days if the forecast holds true. Forecasting 25° here early next week. That's the coldest it's been here for over 10 years.

 

Glow plug harness from 01/15/2004 to 2010

4C3Z12B568AA

For quick reference on parts at wholesale prices using a mobile device I go here: AutoNation Ford White Bear Lake | Parts & Accessories

You can put in your VIN or search by year.

 

Are the above-referenced glow plugs the same as "Motorcraft ZD13 Glow Plug"