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SPN 3251 - FMI 16 (Fault Code 1921)

SPN3251 FMI16
SPN3251 FMI0
Aftertreatment Diesel Particulate Filter Differential Pressure - Data Valid But Above Normal
Operating Range - Moderately Severe Level

ISB, ISC, and ISL - Aftertreatment System



CODES:
Fault Code: 1921
PID(P), SID(S): S324
SPN: 3251
FMI: 0/16
Lamp: Amber

REASON: Aftertreatment Diesel Particulate Filter Differential Pressure - Data Valid But Above Normal Operating Range - Moderately Severe Level. The soot load of the aftertreatment diesel
particulate filter has exceeded the recommended limits.

EFFECT: The check engine light will illuminate. The aftertreatment diesel particulate filter lamp will
flash. Engine protection derate.

Circuit Description:
The engine aftertreatment system monitors the soot load in the aftertreatment diesel particulate filter. Under normal operating conditions, the aftertreatment diesel particulate filter is self-cleaning, where soot is converted to carbon dioxide, nitrogen, and water. Under light load operating conditions, it can be necessary to perform a stationary regeneration of the aftertreatment diesel particulate filter. The soot load in the aftertreatment diesel particulate filter is estimated, using the aftertreatment differential pressure sensor and the calculated soot output of the engine.

This fault code can be triggered if the application is not operating at a duty cycle high enough to actively regenerate the aftertreatment diesel particulate filter. This fault code indicates that the exhaust temperatures exiting the turbocharger are not high enough to actively regenerate the soot that is trapped in the aftertreatment diesel particulate filter. It can be necessary to increase the duty cycle of the application in order to prevent plugging of the aftertreatment diesel particulate filter.

Component Location:
The aftertreatment diesel particulate filter is located in the exhaust system and is installed by the original equipment manufacturer (OEM).

Conditions for Running the Diagnostics:
This diagnostic operates continuously when the engine speed is greater than 500 rpm.

Conditions for Setting the Fault Codes:
The electronic control module (ECM) detects that the soot load of the aftertreatment diesel particulate filter is above normal - moderately severe. The aftertreatment system needs to be regenerated to remove the soot.

Action Taken When the Fault Code is Active:
• The ECM will illuminate the amber CHECK ENGINE light immediately after the diagnostic fails.
• The ECM will flash the aftertreatment diesel particulate filter lamp immediately after the diagnostic fails.
• Mobile active regeneration of the diesel particulate filter will be disabled (stationary regeneration will still be available).
• A moderate torque derate will be applied to the output of the engine (Note: There is no derate in emergency vehicle calibrations.)
• Engine speed will be limited to 1800 rpm (ISB CM2150 engines) or 1500 rpm (ISC and ISL CM2150 engines) (Note: There is no derate in emergency vehicle calibrations).

Conditions for Clearing the Fault Code:
The ECM will turn off the amber CHECK ENGINE light immediately after the soot load in the aftertreatment diesel particulate filter has dropped below the moderately severe level.

Shop Talk:
Verify the electronic control module (ECM) calibration is correct. Check the calibration revision history found on QuickServe™ Online for applicable fixes to the calibration stored in the ECM.
Note: This fault code indicates that the aftertreatment diesel particulate filter requires maintenance by performing a stationary regeneration procedure. This is a maintenance procedure only and is not covered by Cummins Inc. warranty.
Note: Repeated occurrences of this fault code may indicate the engine requires frequent regeneration.

Possible causes of this fault code include:
• The engine has been operating in a light load condition that prevents exhaust temperatures from being high enough to actively regenerate the aftertreatment diesel particulate filter.
• Possible engine failure that causes excessive black soot to be generated.
• If Fault Code 2777 is active along with Fault Code 1921, this indicates that a regeneration inhibit message has been received by the engine ECM and that active regeneration of the aftertreatment diesel particulate filter was not permitted. Confirm that the OEM settings for the aftertreatment permit switch are configured correctly.
• The aftertreatment diesel particulate filter can accumulate an excessive amount of ash in a short time period, due to excessive oil consumption or due to non-combustible elements such as, but not limited to, iron, potassium, or calcium contained in the fuel supply or additives.

The aftertreatment diesel particulate filter soot loading can be classified into four different stages. As the soot load increases, the aftertreatment diesel particulate filter lamp and the Cummins® CHECK ENGINE (Amber) or STOP ENGINE (Red) lamp will operate according to the table below. Inadequate temperature of the exhaust gases entering the aftertreatment system can be a cause of high soot loads in the aftertreatment diesel particulate filter. The duty cycle of the application will need to be increased in order to prevent excessive soot from accumulating in the filter.



Read More:
SPN 157 - FMI 0 (Fault Code 1911)
SPN 411 - FMI 18 (Fault Code 1899)








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