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glow plug controller problems and more

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41K views 13 replies 5 participants last post by  BlackMax Canada 
#1 ·
my truck hasn't been starting well in the cold, found a code saying there's no communication with glow plug controller. replaced the controller and i still have the same problem and code.

also have a fuel temp to high code popping up even below freezing when i first start my truck and my fuel economy display is way off 9.5L/100km or 22mpg and I'm only getting hand calculated 17mpg.

do I have a wiring issue somewhere i cant find?

any helps great, thanks.
 
#2 ·
Iirc the new glow plug control module has to be programmed by the dealer.
 
#4 ·
No programming is needed. When mine went out, R&R'd it and it was like new. If yours is not communicating, there's something else at work...or not in this case. Did you check the relays and fuses to make sure they are all firing?
 
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#6 ·
Did yours throw a code?

Mine has been starting rough but no CEL. The OnStar email I get shows that I have an Engine Issue that needs attention.

I used OnStar they scanned it and gave me P00671 which doesnt exist in the DTC lookup tool (or the tool isnt working) and it was a Glow Plug Module issue.

Gonna be looking into this a little further see if I can reverse seach and try to match up the code they gave me.
 
#7 ·
P0671 is the code for the glow plug on number one cylinder. I didn't even look it up, I just know what it is. If you get P0670, then its the module. The plugs are all numbered 1-8 though.
 
#8 · (Edited)
hmmm pretty sure the dood said P00671 and Glow Plug module which tells me even more that he didnt really know (one extra 0)....so anyway. He did say he cleared his screen before I asked him the specific number....perhaps he was relying on memory.

I'll get it OnStar read again since my cheap reader wont pick it up and EFI is through a buddy which would be a few days. Will confirm before I buy either.

Thanks!
 
#9 · (Edited)
My reference works says open or short in the #1 glow plug control circuit.

Many code readers will not read the codes from any modules except the ECM. That code is from the glow plug controller.
 
#10 ·
redid the OnStar diagnostic

p0671
p0675
p0677

So that is 3 GP's down the passenger side. Wondering if something sinister is going on or just crap luck 3 of 4 on the same side.


Going to search on ways to test (ohm) glowplugs while still in the head.
 
#11 ·
Its possible...but if there was something bad in the plugs then number 3 (P0673) shouldn't be working either. I'm not saying its not possible or maybe the module isn't reading the resistance from that plug, but odds are they're probably toast. For the price of plugs, I would pick up a set of eight and do all eight if you have three that are done.
 
#12 ·
And while you are checking glow plugs, check the wiring for each also.
May have to find a wiring diagram that shows color codes, as I think each one should be a different color.
 
#13 ·
I see methods to bench test the glow plugs, but same method while still in the engine I presume?

Check Ohm between 1 and 5??

Of course we just had our first snow dumping of the year and the truck is a block of ice....will be getting to the testing Wednesday. Have 4 GP's on order and should be here Tuesday
 
#14 · (Edited)
Update:

Rough start below -8Celcius (sputter, cough, ford-ish rattle)
codes (But NO CEL): P0671, P0675, P0677 - Glow plug 1, 5 and 7

Ohm'd all 4 on the passenger side with known codes for 1, 5, and 7 being the bad GlowPlugs. I tested them in the block by removing the wire to each of them and running test leads from block to the lead on the GP on the 0.00 (20k) setting.

#3 being the known good one, it ohm'd out at 0.00 = good

The rest ohm out at 0.12 to 1.00(open) = bad

Removed all 4 of them and bench tested them to confirm. Same results. Surprisingly all 4 came out with little effort and NONE of the tips were flared (having nightmares of the tips staying in the block)

Installing 4 new AC Delco 63G LLY glowplugs as soon as Dad shows up with the parts (thanks dad!)

Torque spec shows 18ft/lbs and a little high heat anti-seize on the treads then I will call it "good"
 
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