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Discussion Starter · #1 ·
Hey guys. First time to posting on the form but really like the information that everyone has shared on this form.

I just bout a 2016 eco diesel with 135K that just had a engine swap to a new 2020 eco Diesel engine replacement (factory installed). I day of purchasing the truck I was driving down the highway and the check engineer light turned on. I went and bought a OBDII scanner (blueDriver) to run a read the code. It came back with a P20EE - NOx Catalyst Efficiency Below Threshold Bank 1. I then looked at the mode 6 data and found that the NOx Catalyst Monitor Bank 1 (PID 98 9A) was reading -20.10%. I cleared the code and the CEL went off. About 30 minutes into my next drive the CEL popped up again. Again same code but this time the sensor read -1.30%.Cleared it again. And again popped back up and the sensor read -1.20%.

At first I thought that it would be a faulty sensor so I live monitored the sensor and it seem to be reporting the right PPM details between the acceptable ranges.

does anyone have any ideas of what could be causing the sensor to read negative and/or what’s causing the P20EE code.

the code is now a permanent code so not able to clear it until a fix is completed.

thanks for the help
89448
 

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2015 Outdoorsman EcoD CC w/6.4' 4X4
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More than likely there is a problem with the SCR itself or the DEF injection. You might want to pull the DEF injector, give it a good cleaning. How old is the DEF in the tank, might be worth cleaning the tank out and start with fresh. Do you know if the previous engine has a failing EGR cooler? it's possible the coolant leaking into the exhaust ruined the exhaust system.
FYI: unless a third party shop retrofited a Gen3 engine into your truck, your '16 has Gen2 engine(same as it left the factory).
 

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Discussion Starter · #4 ·
More than likely there is a problem with the SCR itself or the DEF injection. You might want to pull the DEF injector, give it a good cleaning. How old is the DEF in the tank, might be worth cleaning the tank out and start with fresh. Do you know if the previous engine has a failing EGR cooler? it's possible the coolant leaking into the exhaust ruined the exhaust system.
FYI: unless a third party shop retrofited a Gen3 engine into your truck, your '16 has Gen2 engine(same as it left the factory).
thanks for the quick response. I was thinking along the same lines of checking and cleaning the DEF injector. If that doesn’t work then I was going to move onto the DEF fluid. I don’t know exactly when the fluid was last replenish/flush as the dealer was unsure (sales men didn’t know much of anything about the mechanics).
The EGR hasn’t been replaced and that is my top priority to get replaced on the recall but have been reading that there is really long lead time on the replacement.
I was told that it’s a new third gen motor. I wanted to double check myself but couldn’t figure out where I could pull that info. The mopar sticker on the front shows it was built in 2020.
I’ll clean the injectors now and go from there
 

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thanks for the quick response. I was thinking along the same lines of checking and cleaning the DEF injector. If that doesn’t work then I was going to move onto the DEF fluid. I don’t know exactly when the fluid was last replenish/flush as the dealer was unsure (sales men didn’t know much of anything about the mechanics).
The EGR hasn’t been replaced and that is my top priority to get replaced on the recall but have been reading that there is really long lead time on the replacement.
I was told that it’s a new third gen motor. I wanted to double check myself but couldn’t figure out where I could pull that info. The mopar sticker on the front shows it was built in 2020.
I’ll clean the injectors now and go from there
Its not a third gen engine just a second gen built in 2020
 

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Discussion Starter · #7 ·
Its not a third gen engine just a second gen built in 2020
[/QUOTE
More than likely there is a problem with the SCR itself or the DEF injection. You might want to pull the DEF injector, give it a good cleaning. How old is the DEF in the tank, might be worth cleaning the tank out and start with fresh. Do you know if the previous engine has a failing EGR cooler? it's possible the coolant leaking into the exhaust ruined the exhaust system.
FYI: unless a third party shop retrofited a Gen3 engine into your truck, your '16 has Gen2 engine(same as it left the factory).
thanks for the quick response. I was thinking along the same lines of checking and cleaning the DEF injector. If that doesn’t work then I was going to move onto the DEF fluid. I don’t know exactly when the fluid was last replenish/flush as the dealer was unsure (sales men didn’t know much of anything about the mechanics).
The EGR hasn’t been replaced and that is my top priority to get replaced on the recall but have been reading that there is really long lead time on the replacement.
I was told that it’s a new third gen motor. I wanted to double check myself but couldn’t figure out where I could pull that info. The mopar sticker on the front shows it was built in 2020.
I’ll clean the injectors now and go from there
just finished cleaning up the DEF injector and it was clogged right up. Cleaned it up and we’ll test it out tomorrow.

The permanent code is still there. Hoping it will clear after the trucks been running a bit.
89449
89450
 

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Discussion Starter · #8 ·
Update here... After cleaning the DEF injector I cleared the codes and have been driving it the past two days. On my way back from work the CEL popped back on. Got home and scanned the codes and to no surprise it is the P20EE code. So back to trouble shooting. I completed the Mode 6 scan and again the NOx Catalyst Monitor Bank one returned a value of -4.1%. Any thoughts on what I could do next to trouble shoot before I take it to the stealership.
 

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Discussion Starter · #10 ·
89479

Bore scope down into the scr an look for def buildup.
that would be a good check for sure. But don’t have one unfortunately. I checked inside the SCR before reinstalling the injector and it didn’t look to bad (but I also don’t know the tolerance of the systems). Attached is a photo of the SCR at the injector connection. I removed the built up DEF and reinstalled.
 

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I don't know if this is any help but I got that code at about 4000 miles, checked everything over not wanting to take it to a dealer, found the three bolt flange, the one that the bolts break off, was not tight. Snugged up all the nuts, cleared the code and it has not come back. Someone told me air leaks in the exhaust can cause this code.
 

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As far as a new EGR cooler look at the front of your engine where the injector codes are and see if there is a mark in the right upper corner of the HPFP. should be a white circle i believe. If you have that the engine has the new updated EGR. Anyway that is what they told me when they replaced my engine.
 
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