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Def quality poor, No CEL

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Got the Def quality poor message today. 14 cruze with 220k. Only cel I’ve had a few times is a P2002 for The DPF, but it regens properly and it did not have that code when the countdown came on nor does it have that code currently. Looked at my NOX 1 and NOX 2 readings and will attach photos of those. Sometimes NOX2 was reading higher or the same as NOX 1, other times it was reading lower which seems normal. Any glaring issues with the sensors to anyone? Don’t wanna just Throw sensors at it. Thanks!

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Discussion Starter · #2 ·
I tried this on the highway on my way into work today and neither sensor went below 200 ppm, not sure if this is just the limits of the scan tool or if this could mean both sensors are bad? Going to perform a service regen and reductant fluid quality test per snipesys suggestion after work.
 

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I tried this on the highway on my way into work today and neither sensor went below 200 ppm, not sure if this is just the limits of the scan tool or if this could mean both sensors are bad? Going to perform a service regen and reductant fluid quality test per snipesys suggestion after work.
Maybe you checked already but make sure the SCR catalyst is actually attached to the exhaust :)

Replacing the SCR Catalyst is always a last resort. I hate how GM procedures push replacing things so quickly. Monitoring NOx sensors while driving is not as cut and dry as that document is implying.
 

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Maybe you checked already but make sure the SCR catalyst is actually attached to the exhaust :)

Replacing the SCR Catalyst is always a last resort. I hate how GM procedures push replacing things so quickly. Monitoring NOx sensors while driving is not as cut and dry as that document is implying.
Haven’t checked that but thinking I probably should, just seems odd how the sensors would be reading the same amount of Nox PPM or close to the same, has me thinking either a sensor is lying, or maybe the def injector is clogged?
 

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Haven’t checked that but thinking I probably should, just seems odd how the sensors would be reading the same amount of Nox PPM or close to the same, has me thinking either a sensor is lying, or maybe the def injector is clogged?
Clogged is possible. If you had Gretio you could run a quantity test.
 

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Thought I would update this post. Ran a def injector quantity test and it was functioning fine, went to start car after and it would not start, would barely continue to sputter if I Feathered the throttle. I cranked on it for a very long time before I finally started looking for what could be the problem. The egr was stuck open and was able to get the car started after fixing that. Seems very odd to me how that happened simultaneously with the def injector test. I ended up putting it on a weight reduction. Before I did that I did an oil change as well, had a decent bit of fuel in the oil from what I could tell but I am going to attribute that to how long I cranked on it when egr was stuck. All issues alleviated with the diet. Only current issue now is a random intermittent haze at idle/low speeds, only does it after some city driving. Other than that the car runs great now.
 

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Only current issue now is a random intermittent haze at idle/low speeds, only does it after some city driving. Other than that the car runs great now.
The engine doesn't work corectly without EGR. It can't be tuned out without risking damage. So you'll always get some fuel slipping by.
 

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Gotcha, Assuming that would explain why it usually happens only before the car is fully up to temp. The EGR is still intact but is just unplugged.
If you want to minimize it you can get as high of a cetane as you can… Always use #2/summer diesel if possible, and instead try and get by with additives instead. This is obviously kinda expensive though.

As a general rule #2 runs much better than #1…. Assuming you can get it to start.
 
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