Maybe whatever you swap out is just going to be a band aid fix until it goes in for some possible future dealer recall that'll probably Screw The Pooch
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Bob please post the data you have and any codes that are related.Comment
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Posts are coming up, I have to organize the files first.Comment
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Here are some screen shots of the DEF quality tests. Unfortunately the Verus does not allow to record the entire movie of the test data but here is a data movie of a test drive.Comment
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The movie file must be too big to post here, I'll see if I can get some screen shots of that might be of interest. The codes were P20EE and P2BAD. The codes will clear but the LOW DEF quality message will not and the quality test will not pass.Comment
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I also have these 4 GM documents, The screen shots are on the previous page.Comment
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In a pinch can you just Rube Goldberg, go to the local hardware store, pour in a gallon of distilled water , a gallon of Ammonia, and a shot of Jack?
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Bob here is what I can suggest.
#1 make sure the ecm is at the latest calibration and there is no aftermarket programmer/chip/modules on the truck.
#2 before you run the quality test make sure all codes are erased. make sure the urea tank is at least half fuel, I believe gm says it needs to be at 33% to properly run the quality test. watch the urea pump pressure during the test if the pressure is not within spec the test will fail. the pump pressure is in one of the documents you posted.
#3 if you have not checked yet, you might remove the urea injector and confirm it is not plugged up. you can remove it and command it on with the scanner to check your spray pattern. it should mist it just like any injector. if its spraying poorly it wont mix right and cause the down stream nox sensor to read high or low.
below is a pic of a d-max urea injector that had a poor spray pattern. the white urea crust can simple be cleaned and then retest.
20171103_095053.jpgComment
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I've got a good spray pattern, 3 distinct streams. And it sprayed about 45 ml. in the quantity test.Comment
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I test drove it and tried the test again. the best I can get is about 80ppm on the front sensor and 40 ppm at the rear, and it fails. I have a different cat here (a take off) I'm going to weld in. If you look inside the exhaust right behind the DEF injector you'll see a couple of different diffusers to further mix the fluid into the exhaust stream.Comment
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DEFinitely sounds like a PITA . Hope you're not over analyzing it. How's it test with the air filter out?
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yes there are diffuser plates/bars in there before the filter. if all the conditions to run the test are right and it still fails replacing the filter is the next step. if you have a take off and can try that, that's what I would do. from 80ppm to 40ppm is only a 50% reduction and that's why the test is failing. please keep me posted as its always a learning curve on theses systems. if I remember anything else to help ill post.Comment
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I'm re-running the test now with the different convertor. Data looks better, about 80 and 20 ppm. You can exit the test with the Verus once it's running and it'll still run. Then you can go into the regular data menu and save the test data. We'll see if this passes now. It's interesting, when you watch the data it takes a minute or so to see a response in the down stream N0x sensor after the DEF is injected. It's not an instantaneous thing. Maybe just data lag or a slow chemical re-action ?Comment
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Guess I need to attend The School of Hard NOXwtf leaving the air filter out wont make a difference
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