ISX12/ISX11.9 CM2250 Fault Code: 3649 | SPN: 5024 | FMI: 10Aftertreatment 1 Intake NOx Sensor Heater – Abnormal Rate of Change

Overview

Circuit Description

The aftertreatment intake NOx (nitrogen oxides) sensor is a smart device and communicates with the engine control module (ECM) via the J1939 data link. The aftertreatment intake NOx sensor performs internal diagnostics and reports malfunctions back to the primary ECM using the J1939 data link. The NOx sensor is permanently attached to the NOx control module. They are serviced as a single component and can not be replaced individually. The aftertreatment intake NOx sensor is used to measure the NOx emissions at the intake of the aftertreatment system.

Component Location

The aftertreatment intake NOx sensor is mounted on the engine near the turbocharger turbine outlet.

Conditions for Running the Diagnostics

This diagnostic runs when the aftertreatment diesel oxidation catalyst intake temperature is above 200°C [392°F] for a calibratable period of time while the engine is running.

Conditions for Setting the Fault Codes

The Engine Control Module (ECM) detected the NOx sensor heater was unable to maintain its normal operating temperature.

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.

The engine speed operating range is limited to the adjustable parameter «Maximum Engine Speed without VSS».

Cruise Control, Gear-Down Protection, and Road Speed Governor features will be disabled.

Conditions for Clearing the Fault Code

• To validate the repair, start and operate the engine to raise exhaust temperatures. This can be done by either driving the vehicle or initiating a stationary regeneration using the recommended Cummins® electronic service tool or equivalent.

The aftertreatment SCR outlet temperature must be above 200° C [392° F] for 60 seconds before the aftertreatment outlet NOx sensor can run its internal diagnostics.

• 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

The NOx sensor heater is internal to the NOx sensor assembly, and can not be serviced separately.

Possible causes of this fault code include:

Damaged aftertreatment intake NOx sensor

Intermittent power connection to the aftertreatment intake NOx sensor.

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

For intermittent power supply and datalink communication issues with Aftertreatment Components, it is highly recommended that the OEM Power Distribution Center fuses and relays be thoroughly checked for loose, missing or intermittent connections.