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Discussion Starter #1
Working thorugh this. Posting for other people and selfishly to help myself since searching turns up a few instances of both, but not both on the same start.

Symptoms: Cold start, plugged in block heater for 6 hours (Excessive) knowing I was leaving early in the AM. Temperature was 10F outside. Truck started, CEL was immediate.
P0071 - "confirmed" - (Inlet Ambient Air Temperature)
P205E - "pending" - (intermittent signal from 'reductant' tank temperature sensor circuit (DEF)).

Pulled the air sensor, clean as a whisle. Removed negative cables for 30minutes, still have CEL.

Filled DEF tank, noticed that while key was in ignition position that increasing the ammount of DEF in the tank did not change the needle position (It usually does). Eventually it did start reading full but have not seen it drop since (200 miles later, no DEF usage showing).

Next step: Going to check harness connection on DEF tank. I suppose that is what the little door is on the skid plate.

Not sure what to check next on IAT sensor. Except to replace.

Possibilities:
1) DEF froze and IAT sensor failed at same time, leading to damaged DEF pump since it probably didn't try to heat the DEF? 10F is 2F lower than DEF freezing point. Driven in -2F to 2F weather in the past few days. With cold starts (hunting season in the mountains).

2) Bad wiring harness for DEF (apparently a bad batch around my year of truck?)

3) Apparently there is a TSB that I have seen referenced but not confirmed that addresses P0071 issues, deals with programming the ECU

thoughts?

Will keep you folks posted, been a lurker, time to contribute (and get some help). Local dealer does not get rave reviews, even by their own salesman accounts, so it will be a 150mile trip to the next closest dealer for me (who happens to sell AEV parts so maybe the modifications I've made won't be an issue).

Recent things that changed on the truck in the prior days: Installed ARB compressor and Switch-Pros switch set. Found nearly every fuse somewhat loose in the fuse box. But no electrical issues for many miles traveled on that day. I suppose it is possible that one of the contacts on the bottom of the fuse box got pulled loose also during that install. Looking to see if I can get a hand behind it to push from behind and make sure the wires to the fuse box are all secure. Nothing was done to the truck the day prior to the cold start. I did have a CEL that went away on a hunting trip 2 months ago, never went and read the code and had 30-40 starts on the truck by the time I made it back home not sure it would have showed (2 week trip, communing to trail heads, 2-3 times per day, 6 starts a day probably).
 

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I wouldn't worry too much about the lack of DEF usage, unless you were towing. If I top off my DEF tank, it takes at least a couple thousand miles of empty driving before my gauge starts dropping. One other thing, I don't top-off through the winter because the Def can freeze and (if the tank is full) it won't have any room to expand without possibly breaking something.

There were some updates over the summer that addressed DEF dosing, CEL's & some other issues. If you haven't had that update done, yet, I'd get in there and get the updates.

Jeff.
 

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Discussion Starter #3
I wouldn't worry too much about the lack of DEF usage, unless you were towing. If I top off my DEF tank, it takes at least a couple thousand miles of empty driving before my gauge starts dropping. One other thing, I don't top-off through the winter because the Def can freeze and (if the tank is full) it won't have any room to expand without possibly breaking something.

There were some updates over the summer that addressed DEF dosing, CEL's & some other issues. If you haven't had that update done, yet, I'd get in there and get the updates.

Jeff.
I was not towing, but I was driving the truck pretty hard. 10MPG if that gives you any idea, over 200 miles, not towing. Thanks for the note and advice. I'll post back after I get it looked at.
 

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Discussion Starter #4
well. The truck reset itself...hurmph. I'd rather it just stay broken....have not removed DEF skid to inspect harness at what I assume is DEF pickup point. 200 miles of towing and DEF gauge has not moved (not ususual I suppose if it was indeed full after filling).
 

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Discussion Starter #5
-11 f start but was plugged in all night. Engine sounded good grid heater was not on very long. Back to same codes. Maybe I trust the local dealer with this one.
 
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