Glow Plug Circuit Error P0678
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Glow Plug Circuit Error P0678
I am getting this error code "Error P0678" I believe from reading it is a Cylinder 8 Glow plug problem. Is this a need to fix ASAP or being its 102 deg outside and no end in sight 
can i get to it when time permits and just ignore the light . Thanks for any help 
can i get to it when time permits and just ignore the light . Thanks for any help
Posting Guru
Joined: Oct 2009
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From: Southwest VA
Did you recently wash the engine ?....not sure on a 6.0 but I had a glow plug code after I blew an HPOP oring and had to wash the engine on my 7.3.....water got in the connectors at the valve covers......dryed it out and it went away
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Had a leak from the screw on the heater valve shut off, but thats on the wrong side for a cyl 8 I believe. will check it out thanks. Will this effect the driveability or reliability of the truck while its hot out?
Posting Guru
Joined: Oct 2009
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From: Southwest VA
It should really only affect starting......once its warm it shouldn't matter....plus it is only for cylinder # 8.....so it might miss on # 8 until it warms up......maybe a 6.0 guy can chime in .....put this in the 6.0L forum.....or search there..... They will help you more than general Excursion forum
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From: N.GA Mountains
Ignore the light! 
These trucks WILL start with no glow plugs. In summer, there will be no issues. My trucks will start on 4 GP's down to about 40*, but will smoke a little until engine is warm as it gets colder out.
You can unplug GPCM and check the resistance of the GP's to verify that ya need a GP. Don't use aftermarket GP's, they have a reputation for early failure and 'mushrooming' on the end - making removal very difficult... Motorcraft ZX-11 is what ya want (local autoparts should carry them - $10-12ea). Personally, I would do all (8) if you are removing valve covers.
I was getting a couple GP codes last year, but also (occasional) P0683. I was just about to replace GP's, but decided to try a new GPCM at the last minute. No more codes. (5 min install and $130ish from partsguyed.com)
These trucks WILL start with no glow plugs. In summer, there will be no issues. My trucks will start on 4 GP's down to about 40*, but will smoke a little until engine is warm as it gets colder out.You can unplug GPCM and check the resistance of the GP's to verify that ya need a GP. Don't use aftermarket GP's, they have a reputation for early failure and 'mushrooming' on the end - making removal very difficult... Motorcraft ZX-11 is what ya want (local autoparts should carry them - $10-12ea). Personally, I would do all (8) if you are removing valve covers.
I was getting a couple GP codes last year, but also (occasional) P0683. I was just about to replace GP's, but decided to try a new GPCM at the last minute. No more codes. (5 min install and $130ish from partsguyed.com)
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From: Parma, Idaho
Skyskijason is right except if it is a 6.0 then you will not be removing the valve covers that is only on a 7.3. If you have a busbar that holds all 4 in one metal bar use a catspaw nail remover and work it out all the way across to get all 4 at once. Of course after removing the harness. If it does not have a busbar and is individual glowplugs and you do not have a removal tool I use some baling or other type of wire and double wrap it around the glowplug and twist it together and then wrap a couple wraps around a dowl or stick and give it a good hard jerk straight back it will pop right out. You can start it in cold weather without the no.8 glowplug with seven it will start right up. I currently have 4 out but it is my project Friday to replace them all. And my weather is about 15 at night right now. It should not even run different only thing is just let it warm up before expecting peak performance.
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