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Hello all. Don't post much but I'm hoping some guys in here are familar with these Duramax engines and can give some insight on what I'm dealing with.
Backstory, our local fire dept has this reg cab long box 2013 GMC with the LML in it. They stated one day they noticed on a call that a large amount of smoke was seen leaving the tail pipe. Truck seemed to still have power but shortly after the CEL came on. They had a guy on the dept. (heavy equipment tech) force the truck through a regen and he said all was good. Fast forward to the next fire call and the truck did the same thing. I pulled the truck in and after attempting to force it into a regen I couldn't get the engine temp to operating temp. I had a P0420 CAT code and P01F0 coolant temp code. After some investigation I found the engine temp would only get to 160 and that was it. I found one of the T-stat's was stuck open. Replaced both stats and Purged the cooling system and now I can get it to up to operating temp, I believe it'll get 210 somewhere in there before the cooling fan engages. Anyways, force regen again, truck goes through regen and smokes really bad, figured the truck hasn't gone through a regen in quiet a while since it wasn't getting up to temp. Well it will almost completed a regen but about 3/4 of the way through it'll kick out and my scanner (snap on Zeus) states the Exhaust temp is too low...... I did some more digging and research and we found that the hydro carbon injector was only dribbling a small amount of fuel. Replaced injector and confirmed we were getting proper spray and quantity after the fix.... Forced regen again. Still kicks me out due to low exhaust temp and it still smokes really bad during regen. I watched it closely the last time and Our exhaust temp # 1 will reach 500 F and #2 will reach 900F and when the hydro carbon injector reaches 50% demand the temps drop even lower then that. From my reading this is too low so it kinda points me to this DOC being faulty. I removed temp sensor #2 and stuck a bore scope up there and the back of the DOC looks pretty good but there's no way my scope is going to reach the front of it. Dept. needs the truck and I don't think the city is gonna be happy with the bill or even the quote for a possible DOC replacement. I'm wondering if someone here has some tricks or other things I should be looking at first since I'm kinda new to the tier 4 diesel world. I hate making bad calls and would like to be 100% on my diag.
Overview for guys not wanting to read all of that.
-P0420, P01F0
-Low exhaust temp, failing regen
-New T stat's, new Hydro injector, good spray and quantity
- temp #1 500, temp #2 900 but goes down when injector starts spraying
- backside of DOC looks fine
- A lot of grey/white smoke during regen.
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