ISX12/ISX11.9 CM2250 Fault Code: 3255 | SPN: 3246 | FMI: 16Aftertreatment 1 Diesel Particulate Filter Outlet Temperature – Data Valid But Above Normal Operating Range – Moderately Severe Level

Overview

Circuit Description

The aftertreatment temperature sensors are used by the engine control module (ECM) to monitor the engine exhaust temperatures in the aftertreatment system. The aftertreatment temperature sensors are thermistors and change resistance based on the temperature being measured. The ECM provides a 5 volt reference voltage to the sensor. The ECM monitors the change in signal voltage and converts this to a temperature value.

When the exhaust temperature is cold, the sensor or thermistor resistance is high. The ECM signal voltage only pulls down a small amount through the sensor to ground. Therefore, the ECM senses a high signal voltage or low temperature. When the exhaust gas temperature is hot, the sensor resistance is low. The signal voltage pulls down a large amount. Therefore, the ECM senses a low signal voltage, or a high temperature.

Component Location

The aftertreatment diesel particulate filter outlet temperature sensor is located in the aftertreatment system. It is located at the outlet of the aftertreatment diesel particulate filter. Refer to the original equipment manufacturer (OEM) service manual.

Conditions for Running the Diagnostics

This diagnostic runs continuously when the engine is running and active regeneration of the aftertreatment diesel particulate filter is not occurring.

Conditions for Setting the Fault Codes

The aftertreatment diesel particulate filter intake temperature sensor reading was greater than 687C [1269F] for 90 seconds, or the difference between the diesel particulate filter intake temperature and the diesel particulate filter outlet temperature was greater than 300C [572F] for 90 seconds.

Action Taken When the Fault Code is Active

The ECM illuminates the red STOP ENGINE lamp immediately after the diagnostic runs and fails.

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.

The engine will be shut down if the Engine Protection Shutdown feature is enabled.

Conditions for Clearing the Fault Code

• To validate the repair using a Diagnostic Road Test, utilize a route that incorporates both stop and go city type driving and steady state highway type driving. It may be necessary to load the unit for certain diagnostics in the ECM to run.
• To validate the repair using a Chassis Dynamometer, utilize a routine that incorporates acceleration and motoring events, steady state highway type operation, and load. This will simulate normal driving and allow the diagnostics in the ECM to run.
• 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 red STOP ENGINE lamp immediately after 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

This fault will go inactive immediately after the aftertreatment temperatures drop below the warning limit, and will likely be inactive at the time of diagnosis. For these reasons, this troubleshooting tree must be used for both active and inactive fault codes.

Possible causes of this fault code include:

Excessive engine oil or diesel fuel being introduced into the exhaust system from the engine

A damaged engine fuel injector causing unburned diesel fuel to enter the exhaust system

The aftertreatment diesel particulate filter outlet temperature sensor malfunctioned in-range

A face plugged aftertreatment diesel oxidation catalyst

An in-range engine sensor malfunction has occurred, causing excessive fuel to enter the exhaust system.

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.