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NOx sensor readings

38K views 12 replies 7 participants last post by  truckmen  
#1 ·
Can some one with alpha obd read their nox levels on the input and output of the scr?
Running at operating temperature I get 50ppm inlet, but 4.2 billion ppm on the outlet
I think I have a bad nox sensor on the outlet since the numbers are higher on outlet.
This is also coupled with a U059F code on the replacement sensor
The original sensor threw a P229E.
The voltage to the sensor is good
What are the chances of getting a bad sensor out of the box?
Thanks
Eric
 
#2 ·
It is possible for a bad part. Have you checked the resistance to the outlet Nox sensor? I would do that, as well as shoot pins in all related harnesses. Try to find a wiring diagram. . You can also load test that circuit to verify you do not have a voltage drop causing you erratic voltage reading to Nox sensor. Once you know the wires are good try another sensor. It is defaulting at 4.2 billion. The PACCAR emissions systems have Nox sensors that default at 3000 ppm. It never gives a reading and throws the fault code. Verify proper voltage/ohms on wires and sensor itself, then replace.
 
#3 ·
Yes to the bad sensor. That is what is causing the code. Get it replaced.

2013 2500 6.7 cummins crew cab. white and stock as can be
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#4 ·
or if you do not fix it the next code will be "EGR system shut down" this is what mine did. Truck runs better than it did before the code. I am guessing it goes into some sort of closed loop tune, no change in MPG or power available, pull a dump trailer regularly.
 
#5 ·
And you will get the dreaded 250 mile to derate count down.
Then you will be really screwed.

2013 2500 6.7 cummins crew cab. white and stock as can be
using Tapatalk
 
#8 ·
Mine is in the countdown mode
I think the replacement sensor is bad
New sensor should be here soon
I will report back with readings from alphaobd as soon as I get the new sensor
 
#9 ·
Just do the install and all should reset. It may take a key start cycle or two to clear the code history.
If you had the SCR recall done, you should also check the wiring in the harness on the frame rail for breaks or shorts.

2013 2500 6.7 cummins crew cab. white and stock as can be
using Tapatalk
 
#10 ·
Just a follow up
Replacement sensor was bad
Installed the second new sensor
Inlet is about 90ppm outlet 50ppm
Thanks for all the help
Alphaobd paid for itself today,no way I would have been able to diagnose this without seeing the sensor readings
Thanks
Eric
 
#11 ·
Old topic alert!
Been getting p2201 consistently. I bought this truck in mid October. Drove it 220 miles and got the CEL for NOX circuit 1. 2013 w/122k miles on it. Been clearing the code with AlfaOBD but it just keeps coming back. After reading this post I did a date log of the sensors and am getting odd readings. Start is 0ppm for a bit then I'd get a crazy high number for both then they'd drop to readings in the 220 to 300ppm range for sensor 1 and numbers between 1 and 60ppm for sensor 2. Sensor 2 would read mostly between 8-22ppm tho. When I hit record in the app the numbers would invert and on occasion both would be in the billions...
I was just gonna buy a cheap e-bay sensor for troubeshooting but now I'm not entirely sure the problem is the sensor if both are reading so erratically?
 
#12 ·
Did you figure this out? I'm having the same problem with my 2014 w/ 126k miles. I keep getting a P2201 code and every time I clear it it comes back. and now it's also giving a P1C55 code. Any help would be appreciated! Thanks