P20EE Code on Ram 6.7L Cummins
On a trip to Minnesota (1600 miles round trip) recently my Check Engine Light illuminated on my 2014 Ram 2500 with Cummins 6.7L. This was towing a very light single axle trailer and traveling at interstate speeds. I'm right at 90,000 miles and it's the first CEL I've seen. Of course both of my wireless code scanners were back home so I stopped in an O'reilly Auto and borrowed their scanner.
The scanner showed code P20EE "SCR Oxides of Nitrogen Catalyst Efficiency below threshold (Bank 1)". When I got home I did a bunch of research and found the problem could be a bad NOx sensor, bad catalyst, bad DEF pump, poor spray from urea injection nozzle, or poor quality urea in the DEF tank.
The more I thought I recalled I had last refilled the DEF with cheap stuff from a local farm store (Rural King). Okay, maybe the cheap stuff was too old, poor quality, or had degraded in the tank. So, I stopped at O'reilly and got Peak Blue DEF, siphoned out the DEF tank, and then refilled with new stuff.
While at O'reilly I also bought a new air filter because I realized I hadn't replaced it since I bought the truck last fall. When I opened the air box I almost fell over because it looked like the previous owner never replaced the filter. The intake side of the filter looked like it was dragged through the mud :o I know the previous owner lived about 1/2 mile down a gravel lane so I'm certain there was a lot of dusty air getting filtered.
Since replacing the DEF and air filter I haven't had another CEL. Obviously I can't say if the filter or DEF solved the problem...or maybe neither and the CEL just hasn't come on yet. However, I'm leaning to think the plugged air filter might have been the culprit. My hypothesis is the plugged filter severely restricted air flow and the decreased air:fuel ratio creating poor combustion. That poor combustion resulted in excess NOx formation and the DEF/SCR system couldn't keep up which tripped the NOx sensor.
Thoughts? I've read the P20EE code isn't unique to RAM and that GM and Ford owners with SCR are getting it too.
KJ
The scanner showed code P20EE "SCR Oxides of Nitrogen Catalyst Efficiency below threshold (Bank 1)". When I got home I did a bunch of research and found the problem could be a bad NOx sensor, bad catalyst, bad DEF pump, poor spray from urea injection nozzle, or poor quality urea in the DEF tank.
The more I thought I recalled I had last refilled the DEF with cheap stuff from a local farm store (Rural King). Okay, maybe the cheap stuff was too old, poor quality, or had degraded in the tank. So, I stopped at O'reilly and got Peak Blue DEF, siphoned out the DEF tank, and then refilled with new stuff.
While at O'reilly I also bought a new air filter because I realized I hadn't replaced it since I bought the truck last fall. When I opened the air box I almost fell over because it looked like the previous owner never replaced the filter. The intake side of the filter looked like it was dragged through the mud :o I know the previous owner lived about 1/2 mile down a gravel lane so I'm certain there was a lot of dusty air getting filtered.
Since replacing the DEF and air filter I haven't had another CEL. Obviously I can't say if the filter or DEF solved the problem...or maybe neither and the CEL just hasn't come on yet. However, I'm leaning to think the plugged air filter might have been the culprit. My hypothesis is the plugged filter severely restricted air flow and the decreased air:fuel ratio creating poor combustion. That poor combustion resulted in excess NOx formation and the DEF/SCR system couldn't keep up which tripped the NOx sensor.
Thoughts? I've read the P20EE code isn't unique to RAM and that GM and Ford owners with SCR are getting it too.
KJ
