LBZ Glow Plug diagnosis


New member
Oct 15, 2014
2006 GMC Sierra 3500 SLT duramax 6.6 ... Previous replacements of glow plugs were never a problem.

Now I am getting the po672 glow plug #2 error (#2 is front most on driver side) ... and after replacing it and clearing codes, the po672 pending code comes back immediately.

So I tried a different glow plug, and still the code remained.

At this point I suspected either a wiring harness issue or a glow plug controller module failure ...

So I tried swapping the known working #6 glow plug into the #2 position, since #6 was not getting any error. I put the new glow plug into #6 instead and the working #6 glow plug into #2. The po672 REMAINED (did not move to #6) !!

I have inspected the wiring harness but its quite hard to know if there is a problem. I don't see any obvious problems.

At this point I suspect either a wiring harness issue, or a glow plug controller issue. The glow plug controller on the truck is the 97371413 [ full number on BERU part is 8 9737 14 131 ].

I was going to order a new glow plug controller, as it appears it would be easy to replace ... but I have read in some reviews that you sometimes have to have the deal reprogram the glow plug controller module ... which I was hoping to avoid a pricey trip to the stealership.

I also haven't been able to find a part # for the glow plug harness, and it looks potentially a little more painful to replace.

Advice on how to proceed? I want to sell the truck, but this is causing it fail emissions because of this code ... and thats preventing me from renewing its registration. Truck has been great till now, this is a PITA.

I could also change out all the glow plugs, as I believe I replace most with the old (known to be the best) 4.7v 61g ac delco ... but mainly the new 4.85 ac delco are sold these days. Anways, in my spare parts, I had a 61g 4.7 and also two new 9c glow plugs. I tried both and neither worked to resolved the error code. I suspect both would have worked fine.

What would you do at this point?

Thanks in advance,

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