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Discussion Starter #1
I got in my truck yesterday after sitting for 3 days fired it up took my son to practice. Got back in 2 hours after practice and the CEL came on and it was a P0380 code.
I thought when a glow plug went out it would tell me which one. (ignorant i know) If there was i was wondering if this code is more the glow plug module or a glow plug. I am just going to replace all of them eventually but to fast fix i was wondering what the consensus was. Thanks
 

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Did you check the relays for the glow plug controller?


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Discussion Starter #3
Did you check the relays for the glow plug controller?


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I havent done anything. It was dark last night when i got home and it isnt cold out so it isnt really a worry....yet. Thats where i am going to start though. Get my multi meter out and test the two wires in the plug, pink w/yellow stripe and solid yellow and ohms in my relay if this is correct? Electrical guy im not. I can twist bolts all day...wires ehhhh
 

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I havent done anything. It was dark last night when i got home and it isnt cold out so it isnt really a worry....yet. Thats where i am going to start though. Get my multi meter out and test the two wires in the plug, pink w/yellow stripe and solid yellow and ohms in my relay if this is correct? Electrical guy im not. I can twist bolts all day...wires ehhhh


Is your gpcm a thin sealed unit, or the one with a cover and 2 relays inside?


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I would start with the cheap parts parts first, if you have a test light with alligator clip then clip it on end of glowplug still in engine and touch light on positive battery terminal. If it lights up then it is good, check all 8. Keep in my mind though if the light is barely lit up that the glowplug is weak and needs replaced anyway. Use acdelco glowplugs only, others are garbage. If they all check out then proceed to check relays.

For checking relays and wiring there is a very informative video on youtube for going through the process of checking all the control circuits and components. Type in 2001-2004 Duramax LB7 P0380 Code by Hatecke007

Good luck!
 

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Discussion Starter #8
Is your gpcm a thin sealed unit, or the one with a cover and 2 relays inside?


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Funny you ask, w/o looking i ordered the one with the cover because when i googled the part for the LB7 it mostly showed the one with the cover. Well thats not the one i have. That would be the thin one with 3 plugs
 

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Discussion Starter #9
Ever figure this out? Just wondering because mine has been showing the same code off and on but effects really nothing. Just curious
No, I just sent the wrong part back (gpcm with the cover). I am going to order the thin flat one. I did check the glow plugs they all test good. The truck does not run bad at all. I live in SoCal so i guess if it were cold outside it might have issues starting in the cold but that is not the problem. The light on is my problem
 

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Ever figure this out? Just wondering because mine has been showing the same code off and on but effects really nothing. Just curious
Did you ever figure your code out. I have now replaced the glow plug module and all 8 glow plugs and still having the code return but truck runs fine. Next i guess i will be checking voltage at each plug.
 

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Here’s a quote from the link I posted earlier:

I did it I cracked the p 0380 code on my duramax, I changed the module and that didn’t work, so I took a hunch on the 175 maga fuse. My truck was knocking really bad had no power. Once I change the fuse it stop knocking and started running smooth transmission was shifting better but after shutting it off multiple times and starting . Service engine light shut off. And the truck runs so much better. I hope this helps you all a simple fuse Really put the hurt on my truck and my mind hope this all helps you.

Read more at: https://www.obd-codes.com/forums/viewtopic.php?t=13650
Copyright OBD-Codes.com
 

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Discussion Starter #12
So after chancing this dragon for 2 weeks i finally figured out what happened. I had the initial code pop up about a month ago. I replaced the controller (because it was the easiest way out) the code never went away. I purchased new GP's and replaced all 8. The code was gone for about 4 days. Then the code would come on at first start of the day and turn it self off during multiple starts during the day but would come on everyday at first start. I finally had time to check Ohms in all 8 GP's The plug behind the steering shaft was a little loose and was not grounding itself very good and causing the code to pop up. I tightened that one (at the time i was afraid of over tightening and it was hard to get to) and went back and checked all others. With no excuses it all comes back to my fault, with a little aggravation i was able to track it down and fix the issue.

Just an FYI for those DIY'ers
 
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