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Discussion Starter #1
Looking for some help here. I have a 2016 lml duramax. I keep getting a p0672 code for #2 glow plug. I have replaced the plug with no change. I load tested the wire and also ohm tested it. All is good with the wire. Installed new glow plug control module and still keep getting the same code. Also if I unplug another glow plug it does not throw a code. Anybody have any ideas as to what could possibly be my issue. I have exhausted my thoughts and options to come up completely clueless on what else it could be. Also scan tool shows on test that all glow plugs pass and self check ok. But still have a mil light and code coming up.
 

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Here are the test instructions for my 2008 model. I THINK you've covered the testing correctly, but check to be sure

  1. Ignition ON, and the glow plugs not commanded ON, probe the affected glow plug with a test lamp connected to ground. Observe that the test lamp does not illuminate.
  • If the test lamp does illuminate, test the glow plug control circuit for a short to voltage or for a faulty glow plug control module (GPCM). Replace the affected glow plug after repair.
  1. Ignition ON, probe the affected glow plug with a test lamp connected to ground. Command the glow plugs ON with a scan tool and observe the test lamp. The test lamp should illuminate.
  • If the test lamp does not illuminate, test the affected glow plug harness between the glow plug control module and the glow plug for an open, short to ground or high resistance.
  1. Ignition OFF, and the affected glow plug disconnected, measure the resistance between the affected glow plug terminal A and ground with a DMM for less than 1 ohm.
  • If the resistance is more than 1 ohm, replace the affected glow plug.
  1. Ignition OFF, and the glow plug control module harness disconnected, measure the resistance between the affected glow plug harness connector terminal A and the corresponding glow plug control module harness connector terminal for less than 1 ohm resistance.
  • If the resistance is more than 1 ohm, repair the harness.
  • If the resistance is less than 1 ohm, replace the glow plug control module.
Component Testing

With the igniting OFF and the affected glow plug disconnected, measure the resistance between the affected glow plug terminal of the glow plug and ground with a DMM for less than 1 ohm.

If the resistance is more than 1 ohm, replace the affected glow plug.
 

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Discussion Starter #3
Rechecked my steps and all the same. Glow plug tests good and wiring to plug is also good. Still same issue. Another thing I noticed is if I unhook another glow plug it will not throw a code for it. But scan tool test will show a malfunction for it. Is there a fuseable link in the engine wiring harness or anything? I found before that the harness rubbed through at the ac compressor and 1 wire was a power wire to the glow plug module. Does anyone happen to have a wiring breakout diagram for the glow plug module that I could happen to use to help diagnose this issue? I am almost wondering if replacing the engine harness will solve my issue.
 

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Discussion Starter #5
Thanks for the info. I was able to find the schematic and do a complete test on the wires. But unfortunately I did not find anything wrong with the wires. Looks like my ecm must have an internal issue that I have to have fixed now. Not what I was hoping as the truck is all tuned.
 
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