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I have 2011 duramax. A couple of weeks ago I had my def poor quality message come on. I followed the owners manual guidelines added 2.5 gallons fresh, drove down the highway 20 miles and the light cleared. I have not any problems for over 500 miles. This morning driving to work the message came back. The mil check engine is off and no codes found. Ambient temp this morning was 30. Does any one have ideas what is going on? Is there way to turn this light off ?
 

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Likely needs 1 or both NOx sensors replaced.

Likely there was nothing wrong with your fluid, and light went out because the sensor is on the borderline good/bad.

Depending on mileage, the sensors on the 11 could still be covered under the enhance warranty GM offered for the '11's -- need to have VIN checked to confirm.


I'm surprised you didn't find all this out using the 'search feature'. It's the most common topic on this forum, there are 100's and 100's of posts about it.
 

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Thanks for your reply. I have not figured out how to use this forum and get most out of it. It is bit overwhelming in size. I got def light to go out several times by driving down road at 65 to 70 mph in 4th or 5th gear to bump up the rpms only to have reappear a week or so later . My scan tool is now showing a pending code P20EE scr NOx catalyst efficiency below threshold. Do you still believe it the sensor. I think I am past the enhanced warranty period and will have go at it alone.
 

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Are you above 120,000 miles?


Yes, I still suspect the sensors.
If it is one or both NOx sensors, I think you'll need dealer electronics to do the calibration process for the new ones.
 

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I had many DPF issues. My warranty ran out, and honestly couldn't afford paying a GM tech to figure it out. I deleted DPF/EGR 35000miles ago. Best decision I've made for the truck.
 

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First of all the error messages are not going to accurately reflect the problem with the engine and emissions system. Most likely the truck needs a full regen of the particulate filter and this can only be done by the dealer as a "service regen". They can put the truck into service regen and then run the engine at high idle for as many hours as it takes to clean the filter. With my truck they burned through roughly 10 gallons of diesel.
 

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DPF and DEF systems operate independently of each other. The only thing they share is the actual physical exhaust pipe. Based on the code sounds like you either actually have bad fluid (I have seen bad fluid out of the container) or a failing sensor 2. You could also have a def injector issue but I don't see those very often. If it is the sensor they aren't cheap and there is a reset procedure that requires a scan tool.
 

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I had many DPF issues. My warranty ran out, and honestly couldn't afford paying a GM tech to figure it out. I deleted DPF/EGR 35000miles ago. Best decision I've made for the truck.
Thats great, but MANY these days live in smog counties. The “delete” suggestions frankly get OLD...
 

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Like mentioned its more than likey NOx sensors. Very common on 2011/12 trucks. I just had to have mine replaced at 125kmi (just out of warranty...). Take it to the dealer unless you really know what your doing.
 

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after reading everything i am really thinking about a delete what i want to know is what all will have to be done
other than a programmer and i think a new exhaust anything else thanks for your help in advance also any particular brand of programmer
 
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