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Discussion Starter · #1 ·
I’m “almost” at a loss.
truck info : 2011 Sierra Denali 2500 edge tuned and dpf deleted.
location : MN Snowy and cold
Replaced: transmission filters, NSBU switch

all the stories short:
Hooked up boss v plow. Plowed twice. Second time out, went in to limp mode sporadically. Pulled codes p0700 p0708 and p0706. Keep in mind it would randomly do this. Some days the truck ran and shifted great, then some moments it didn’t. I read a lot and and usually figure things out. Buddy(diesel mechanic) looked into with expensive scanner. Couldn’t really tell. Everything I read pointed to the nsbu switch but didn’t think that was it because it would still always go into gears, until a couple days ago it didn’t. BOOM thought I nailed, Had him put a new one in and did all the filters and blah blah while he had to drop the pan. Drive it home, it wasn’t until I left again it slammed into reverse then wouldn’t go in to gear again. I remembered something important at this time. My truck in the morning would read in the 10-11.5V range (had both batteries load tested and were good, alternator was good, it all tested good)(could be wrong, it is oreillys load testers after all…) which he didn’t seem to be concerned, through research to find that it is a big deal… figured maybe one of the plow wires or LED wires was drawing power or something wasn’t right or whatever. So I got out disconnected both batteries, unhooked all the plow and lights wiring, did a hard reset touching the battery ends together(which I was told wouldn’t effect the efi live since it was deeper internally), ran great. Still having that wiring disconnected, now today my truck is doing its normal idle adjustments, but almost constantly and the voltage is ranging from 13.5 - 15.3 v while driving (not sure if that’s normal but from what I’ve read over 15 isn’t usually good..). Now when I was driving I noticed weird shifting at times. And now when I shift into drive she clunks. One thing I haven’t checked is grounds, which look pretty rusted and corroded under the door. But I can’t help but think of the timing. Hooked up plow first snowfall, ran great. Hooked up external led lights for added light before second snowfall. During plowing that second snowfall is when all the problems started happening. I hooked up the LEDs to the plows solenoid(not sure if that’s too much for it but I doubt it). I’m open to ideas obviously and we have three straight days of snowfall coming up and I need to be able to trust this thing ASAP!!! Thanks guys I could probably type more but we will start here
 

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Rather than give a laundry list of concerns, what is your most pressing concern?

now today my truck is doing its normal idle adjustments, but almost constantly and the voltage is ranging from 13.5 - 15.3 v while driving (not sure if that’s normal but from what I’ve read over 15 isn’t usually good..).
Don't worry about this. After plow season, you can look at it. Cold weather brings higher charging voltages.

2011's were infamous for bad TCM's. That MAY be the cause of your DTC's
 
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Discussion Starter · #3 ·
My main concern is to not have any issues. I wanted to post absolutely everything I could think of in case something specific may spark an answer. It seems like if I shift into gear before the gauge reads 15v it’ll go into gear. The truck has been running fine for 3 days now, and when it won’t go into gear is when I leave it sit idling in park, but even then, now, I usually just have to turn the key off and on once and put it into gear for it to work. No funky shifting or anything, just that beginning putting it in to gear. Idk could be the tcm I suppose. It’s not tight to the front wall I just noticed and I’m sure it’s been bouncing around.
 
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