Fault Code 3749 on ISX15 2350
09-23-2020, (Subject: Fault Code 3749 on ISX15 2350 ) 
Post: #1
Fault Code 3749 on ISX15 2350
I've been hauling beans from the field to the elevator the past few days and late this afternoon I got a check engine light on my dash. I had my laptop and NEXIQ with me so I plugged in and the code was 3749. I reset it but the light came on again within 20 miles. The code states that the Aftertreatment NOX Sensor Not Rational - Drifted High.

What is the process here? Do I simply replace the sensor?

Truck has 329,000 miles. In the past 5,000 miles I've replaced the Delta-P, IMAP, and Exhaust Gas Pressure sensor. I also inspected the doser and it appeared clean.
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09-24-2020, (Subject: Fault Code 3749 on ISX15 2350 ) 
Post: #2
RE: Fault Code 3749 on ISX15 2350
Go to quickserve.com and open an account with your engine serial number it's free. Next you click on the service tab and youll see a place to enter that code you got(3749) it will tell you conditions for setting that particular code and "shoptalk"will tell you possible causes. Click on "troubleshoot code 3749" and it will take you to a series of troubleshooting steps.
That's where you need to start. If you have questions or get stumped come back here and post what problem you ran into.
Blindly throwing parts at it can get expensive, ^^^^ this is a better way


User's Signature: Warranty??? Yeah right, I am the warranty!!!
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 Thanks given by: Rawze
09-24-2020, (Subject: Fault Code 3749 on ISX15 2350 ) 
Post: #3
RE: Fault Code 3749 on ISX15 2350
Thanks Tree. I've reviewed the info on Quickserve. The problem is either a bad sensor or a plugged decomp tube. Will I cause any issues running it this way for a few weeks (low mileage)?
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09-24-2020, (Subject: Fault Code 3749 on ISX15 2350 ) 
Post: #4
RE: Fault Code 3749 on ISX15 2350
I don't think it will regen in the condition it's in now so you will be plugging up the dpf, especially with a lot of idleing. What's the Aftertreatment history look like in insite? Are the numbers on the far right averaging above 3.0 ?


User's Signature: Warranty??? Yeah right, I am the warranty!!!
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09-24-2020, (Subject: Fault Code 3749 on ISX15 2350 ) 
Post: #5
RE: Fault Code 3749 on ISX15 2350
(09-24-2020 )Golfnut Wrote:  Thanks Tree. I've reviewed the info on Quickserve. The problem is either a bad sensor or a plugged decomp tube. Will I cause any issues running it this way for a few weeks (low mileage)?

maybe inspect inside the decomp tube as well..
http://rawze.com/forums/showthread.php?t...07#pid1807


User's Signature: ->: What I post is just my own thoughts and Opinions! --- I AM Full Of S__T!.
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09-24-2020, (Subject: Fault Code 3749 on ISX15 2350 ) 
Post: #6
RE: Fault Code 3749 on ISX15 2350
I inspected the decomp tube with an inspection camera and the screen appears clean. The tip of the doser had some buildup so I clean it off. I'm running a forced regen now and it said it was dosing. All my numbers on the right side of the history chart were under 2.
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 Thanks given by: Rawze , tree98
09-24-2020, (Subject: Fault Code 3749 on ISX15 2350 ) 
Post: #7
RE: Fault Code 3749 on ISX15 2350
The regen finished in just over an hour with a differential of .9
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09-24-2020, (Subject: Fault Code 3749 on ISX15 2350 ) 
Post: #8
RE: Fault Code 3749 on ISX15 2350
Its a good bet it's the nox sensor.


User's Signature: Warranty??? Yeah right, I am the warranty!!!
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