SCR Diagnostics with Tailpipe Analysis

[@adamrobles6355]

Holy cow I’m a Ford diesel tech and I’ve alway asked our engineers to explain why I always see high nox on the out and low on the inlet . Never could get a straight answer but you come and explain it easily I’m so mind blown right now. Thanks for the awesome video keep it up!

[@joediagnostics]

Glad you like it, Adam. Thanks for the comment, and compliment.

[@adamrobles6355]

@@joediagnostics buy chance do you have video or info on how to diagnose a skew nox 11 sensor when they set P2201?

[@joediagnostics]

@@adamrobles6355 ​ @Adam Robles I'd check it 2 ways. First do a hard decel, so you hit injector cutout. Both NOx sensors should go to 0 ppm. I replace any sensor that doesn't go under 15-20 ppm. See this video. We do the decel check in it: kzbin.info/www/bejne/en2pdaCcadlja9k If you have a gas bench, unplug the DEF injector. drive it and NOx sensors 1 and 2 and the gas bench will all agree on NOx level.

[@michaeldarcangelo3109]

Fantastic video

[@joediagnostics]

Thanks!

[@nickayivor8432]

Very KNOWLEDGEABLE Thank you very helpful video 👍 👌 Joediagnostics From Nick Ayivor from London England UK 🇬🇧

[@jesusbaca184]

Awesome video but is there a preference for when you test this? Such as at idle or during road test or maybe during regeneration? I think it wouldn’t matter as long as it’s a 90% efficiency rate right ?

[@joediagnostics]

If the system is hot an operating, you're right. It should always be 90% reduction. if you're looking for DEF crystals sublimating (boiling) off, then it will have to be under heavy load, or during a regen/scr test. The exhaust has to be really hot for that.

[@gcmd5852]

Nice work, Great information.

[@chekelley6861]

Isn’t the SCR the component that converts urea into ammonia in the first place? The ammonia then reacts with the NOX to degrade into inert gasses. If there was a total SCR failure, you should just have raw urea? Am I figuring this wrong?

[@joediagnostics]

The SCR doesn't convert the urea to ammonia, it's just the heat in the exhaust that does it (also isocyanic acid, then more ammonia). That's why they have a decomp tube in them, to blend the urea with the hot exhaust gasses and allow time for the reaction to take place.

[@chekelley6861]

@@joediagnostics that makes sense. I’ve never completely understood that process.

[@jesusfirstc]

Awesome video

[@joediagnostics]

Thanks!

[@ronunderwood5771]

Do the NOx sensors on the Cummins engines in the medium and HD trucks work this way? Thanks

[@joediagnostics]

Sure do. They work that way on every diesel.

[@ronunderwood5771]

@@joediagnostics Very useful to know. I’ve had a fair amount of training in after treatment and this has never been shown . We don’t see many SCR codes but w/o knowing this you could get pretty far in the weeds. Thank yo for the reply.

[@gcmd5852]

Did i read somewhere you said snap on commercial division offered a Nox only meter? If so do you have an item number? Thanks

[@joediagnostics]

HHGANOX1

[@gcmd5852]

@@joediagnostics Could it have been discontinued? That number didn't come up, Snap on guy couldn't find it either. Thanks

[@joediagnostics]

​@@gcmd5852 kzbin.info/www/bejne/sHXLZ6dsmruZodU It's a current part number in the US with the commercial and industrial guys.

[@joediagnostics]

You are correct. So sorry for not seeing this sooner. It is HHGANOX1.

[@erikcarpenter7860]

What does a failed SCR look like on the inside?

[@joediagnostics]

Hey Erik. In my experience they look completely normal. Of course sometimes they are full of soot if the DPF comes apart.

[@erickramirez5835]

how far can you run the vehicle when you get that problem?

[@joediagnostics]

It depends on the vehicle, but most derate in under 100 miles

[@trainer2018]

What part number is the anaylizer?

[@bobcreque]

HHGA5C or HHGA5CP

[@narekhart9862]

Nugget