Overview

Code

Fault Code: 1879

PID: S324

SPN: 3251

FMI: 3/3

LAMP: Amber

SRT:   

Reason

High signal voltage detected at the aftertreatment differential pressure sensor circuit.

Effect

Possible reduced engine performance.

Aftertreatment Diesel Particulate Filter Differential Pressure Sensor Circuit

Circuit Description

The engine control module (ECM) provides a 5 volt supply to the aftertreatment diesel particulate filter differential pressure sensor on the sensor supply circuit. The ECM also provides a ground on the sensor return circuit. The aftertreatment diesel particulate filter differential pressure sensor provides a signal to the ECM on the aftertreatment diesel particulate filter differential pressure sensor signal circuit. This sensor signal voltage changes, based on the differential pressure across the aftertreatment diesel particulate filter.

Component Location

The aftertreatment diesel particulate filter differential pressure sensor is mounted on the diesel particulate filter. It is a combination sensor that detects both diesel particulate filter differential pressure and outlet pressure. Refer to the original equipment manufacturer (OEM) service manual.

Conditions for Running the Diagnostics

This diagnostic runs continuously when the keyswitch is in the ON position or when the engine is running.

Conditions for Setting the Fault Codes

The Engine Control Module (ECM) detected the aftertreatment diesel particulate filter differential pressure signal voltage was out of range high.

Action Taken When the Fault Code is Active

• The ECM illuminates the amber CHECK ENGINE lamp and/or the malfunction indicator lamp (MIL) immediately when the diagnostic runs and fails.
• A default value for the aftertreatment diesel particulate filter differential pressure is used.
• Diesel exhaust fluid injection into the aftertreatment system is disabled.

Active and stationary regeneration of the diesel particulate filter will be disabled.

Exhaust gas recirculation (EGR) valve operation will be disabled.

Engine torque will be reduced if the engine is operated for an extended period of time with this fault active.

Conditions for Clearing the Fault Code

• To validate the repair, perform a key cycle, start the engine and let it idle for 1 minute.
• The fault code status displayed by the recommended Cummins electronic service tool or equivalent will change to INACTIVE immediately after the diagnostic runs and passes.
• The ECM will turn off the amber CHECK ENGINE lamp immediately after the diagnostic runs and passes.
• For On-Board Diagnostics (OBD) engines, the ECM will extinguish the Malfunction Indicator Lamp (MIL) after three consecutive trips where the diagnostic runs and passes.
• The “Reset All Faults” command in the recommended Cummins electronic service tool or equivalent can be used to clear active and inactive faults, as well as extinguish the MIL for OBD applications.

Shop Talk

Possible causes of this fault code include:

• Open return circuit in the harness, connectors, or sensor

Signal circuit shorted to sensor supply or battery voltage.

Reference the appropriate OEM wiring diagram when troubleshooting circuits that utilize wiring supplied by the OEM.

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