KC-107

8/31/2021
Article
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Selective Catalytic Reduction ( SCR ) Efficiency And
NOx Sensor Diagnostic Trouble Codes ( DTC )
P225C, P225E, P221A and P2201: NOx Sensor
Diagnostic Information TO BE USED BEFORE
SENSOR REPLACEMENT - OBD13 And Newer
Emissions (Commonly Model Year 20
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Internal Content
DO NOT REPLACE EITHER NOx SENSOR FOR ANY OF
THE FOLLOWING CODES (P2201, P221A, P225C,
P225E, P20EE, P207F, P103C) PRIOR TO REVIEWING
THE INSTRUCTIONS BELOW
The purpose of this article is to prevent unnecessary component
replacement. ALL OTHER DIAGNOSTIC TESTS AND CHECKS MUST
BE PERFORMED when diagnosing one of the codes above if the
tests below do not immediately reveal an issue.
If an eService case must be submitted, ALL
INFORMATION specified in Step Five MUST be included at the
time the case is opened. Cases missing required information will
be Refused.
Overview
Guided Diagnostics for SCR efficiency or NOx sensor fault codes will
often result in No Fault Found. This often leads to replacement of one
or both sensors despite no indication from diagnostic steps to do so.
NOx sensor function is a possible cause, and is listed as such for the
code description in the DTC description in Premium Tech Tool ( PTT ).
However although the sensors themselves are a possibility, NOx
sensor codes are most often a symptom, not a cause of
emissions issues. NOx sensors should be confirmed to be reading
incorrectly or functioning erratically before they are replaced.
Fault Codes
A complete list of DTCs related to this Solution can be found in the
Fault Codes section below.
UI
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Procedure
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- Review the Detailed Status Information for the relevant code
on the DTC Readout.
• If Confirmed DTC is TRUE: Proceed with diagnostics
• If Confirmed DTC is FALSE: Disregard and focus on other
symptoms or DTCs relevant to the complaint.
- A NOx Conversion should be run to check NOx sensor signal and
function for any of the above codes.
NOTE: A NOx conversion test only checks NOx sensor function. The
test compares the readings of the two sensors as the engine cycles
through multiple conditions to confirm they are in agreement. The
results of the NOx Conversion test do not indicate anything
about the condition of the SCR itself.
1. In PTT, run Operation 2549-08-03-03 NOx Conversion, located
under the Test tab.
2. While running the routine if you get new NOx sensor fault code
(Egs: P220E-93 , P220F-93), then troubleshoot that fault code.
Typically P220E-93 fault code suggests replacement of NOx1
sensor.
3. Take screenshots of the graph and sensor values approximately
2-3 minutes prior to engine shutdown. A guide to taking
screenshots can be found in THIS solution.
- Inlet and Outlet NOx values should be within 40 parts per
million (ppm) of one another just before the engine shuts down.
Shown below is an example of how a graph with two properly
Live
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functioning sensors will look:
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4. If no issues are found with the sensor readings from the NOx
Conversion review, the sensors are not the source of the
conditions causing the codes to log. Further diagnostic steps of
other components will need to be performed to determine the
cause of the faults.
5. If this solution is being reviewed for P20EE, P207F, P225E or
P103C, the DEF Dosing Valve Solution for the same DTCs should be
reviewed for further information.
6. If diagnostic steps do not locate a root cause for the code(s),
open an eService case with Dealer Technical Support
- The screenshot(s) taken of the NOx conversion screen prior to
engine shutdown (as shown in the screenshot above) should be
attached to the case.
- A complete summary of all tests performed along
with numeric measurements, a DTC Readout, and any
information concerning previous visits and parts replaced must
be included when the case is opened.
• "Ok", "Good" and "Followed GD" are not acceptable
descriptions of tests performed and test results.
- Add the solution numbers for all CBR articles followed.
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Tags
k15560422
p225e-00
p2201-64
p220164
p221a-00
p221a00
p225c-00
p225c00
p225e00
Related links and attachments
KC-104
KC-908
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