My truck pulled a new one on me today; P20EE: "SCR oxides of nitrogen catalyst efficiency below threshold (bank 1)."

Is it something to worry about? I was just at my service center today and would prefer not to have to rush back. I've heard various things from Dodge and other diesel guys saying it's got to do with the DEF (which I just thought I filled) and is nothing but a nuisance, and then I've heard it's the NOx sensor and whatnot.

 

P20EE - SCR NOX Catalyst Efficiency Below Threshold (Bank 1)
<TABLE border=1 cellSpacing=0 cellPadding=3><TBODY><TR><TH vAlign=bottom align=middle></TH><TH vAlign=bottom align=middle></TH><TH vAlign=bottom align=middle></TH><TH vAlign=bottom align=middle></TH><TH vAlign=bottom align=middle></TH></TR><TR><TD style="BORDER-RIGHT: medium none" vAlign=top align=left>Description: </TD><TD style="BORDER-LEFT: medium none" vAlign=top colSpan=4 align=left>The efficiency of the selective catalytic reduction (SCR) catalyst to remove nitrogen oxides (NOx) from the exhaust gas is calculated based on an upstream estimate and the downstream measurement. The concentration of NOx upstream of the SCR catalyst is an estimate based on a calibrated model. The concentration of NOx downstream of the SCR catalyst is measured with the NOx sensor. This DTC sets when the SCR catalyst efficiency is below a calibrated threshold for a calibrated amount of time. </TD></TR><TR><TD style="BORDER-RIGHT: medium none" vAlign=top align=left>Possible Causes: </TD><TD style="BORDER-LEFT: medium none" vAlign=top colSpan=4 align=left>

• Reductant quality
• SCR catalyst low efficiency
• Damaged SCR catalyst

</TD></TR><TR><TD style="BORDER-RIGHT: medium none" vAlign=top align=left>Diagnostic Aids: </TD><TD style="BORDER-LEFT: medium none" vAlign=top colSpan=4 align=left></TD></TR><TR><TD style="BORDER-RIGHT: medium none" vAlign=top align=left>Application </TD><TD style="BORDER-LEFT: medium none" vAlign=top align=left></TD><TD vAlign=top align=middle>Key On Engine Off </TD><TD vAlign=top align=middle>Key On Engine Running </TD><TD vAlign=top align=middle>Continuous Memory </TD></TR><TR><TD style="BORDER-RIGHT: medium none" vAlign=top align=left>All </TD><TD style="BORDER-LEFT: medium none" vAlign=top align=left></TD><TD vAlign=top colSpan=3 align=middle>GO to Pinpoint Test RD . </TD></TR></TBODY></TABLE>


Could be bad DEF or the NOx sensor.....

I would just drive it and see if it goes away

 

Thanks, I appreciate this. I had heard about the bad DEF but my last fill was partly at a truck stop and then with BlueDEF, so I'm guessing that's unlikely. I'm really hoping this just goes away.

 

I've had a few sprinter vans where the injector port on the exhaust plugs up (the same supplier handles both systems and are very similar). But my first guess would be it's more a sensor issue.