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Herky, jerky take off from idle.

1K views 4 replies 2 participants last post by  Papaloco 
#1 ·
2008 F450 with 85000 miles and got my first check engine light, P0684 the Glow plug module to PCM communication circuit range/performance. Saw some earlier posts on this, but none for my year/engine. Whats it mean? Also have a herky, jerky take off on light throttle pressure take offs. Back off or step harder and it normally goes away. All this while pulling a 12,000 lb fifth wheel. Any ideas?
 
#2 ·
Ford must have engineered these things to all go out at the same time. I had the same code on my 08, but I have 145k. Need to replace the glow plug control module and it should clear the code right up. Super easy job to do as it just sits on top of the engine back by the firewall on the passenger side. I ordered my OEM module from Amazon for a little over $100.

Not sure about the jerky takeoff. Maybe someone else might be able to chime in.

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#3 · (Edited)
Which part?

Amazon shows a switch which I believe is the one you replaced and a controller. Which one did you replace to get rid of that code? As for that jerking I noticed it while using a Banks tuner and pulling the trailer. I think it's the accelerator pedal switch and the Banks tuner just points it out due to the tweaking.
 
#4 ·
Amazon shows a switch which I believe is the one you replaced and a controller. Which one did you replace to get rid of that code? As for that jerking I noticed it while using a Banks tuner and pulling the trailer. I think it's the accelerator pedal switch and the Banks tuner just points it out due to the tweaking.
Motorcraft DY876 Glow Plug Switch



That's the one I installed. I also went and purchased the heat shield from the dealer as mine didn't have one..I think that was $15. I figured that might help shed some of the heat since it sits there right near one of the turbos. Replacement of the module involves 3 nuts and unplugging two cables. Can't get much easier than that.


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