Truck not using def
Tuned
Joined: Jan 2023
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Lead Driver
Joined: Nov 2005
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Scant info, need more, miles driven, loading etc.
If you aren't towing, hauling heavy, then a full tank of DEF won't start showing any use on the gauge for over a thousand miles.
The gauge is not linear like a fuel level gauge, and there is well over a gallon above the full mark when filled to the top.
If you aren't towing, hauling heavy, then a full tank of DEF won't start showing any use on the gauge for over a thousand miles.
The gauge is not linear like a fuel level gauge, and there is well over a gallon above the full mark when filled to the top.
Lead Driver
Joined: Nov 2005
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You mean tow/haul?
Regeneration cycles are not dependent on having anything turned on, it is a process that is set to occur at certain intervals for self maintenance or when the DPF gets a high enough load of soot built up.
Also, regen cycles have nothing to do with DEF usage, two separate systems.
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Super Moderator
Joined: Aug 2008
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From: Frederick, MD
when not towing, every little def is used.
when towing, def is significantly increased.
Selecting tow haul mode or any other mode does not do anything to increase def usage.
Part II:
Regen is independent of DEF usage. regens are more unload vs heavy towing.
Regen is done either active (PCM initiates and process) or passive.
Passive regens happen more so with heavy towing.
So with heavy towing more def is used and fewer regen events that you will notice. Passive regens are happening but not noticed.
when towing, def is significantly increased.
Selecting tow haul mode or any other mode does not do anything to increase def usage.
Part II:
Regen is independent of DEF usage. regens are more unload vs heavy towing.
Regen is done either active (PCM initiates and process) or passive.
Passive regens happen more so with heavy towing.
So with heavy towing more def is used and fewer regen events that you will notice. Passive regens are happening but not noticed.
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Lead Driver
Joined: Feb 2005
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From: The Great State of Texas
If your truck wasn't using any DEF, it would trigger a CEL and/or put the truck into limp mode after 50 miles due to out of specification Nox levels.
Super Moderator
Joined: Aug 2008
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From: Frederick, MD
I would not confuse the system by adding when not needed. Rather run it down till you get the <200 miles to empty, then do a complete fill.
IMHO, it helps keep it from being confused.
There are others that do thing differently though.
IMHO, it helps keep it from being confused.
There are others that do thing differently though.