B6.7 CM2450 B155B Fault Code: 6781 | SPN: 4765 | FMI: 21Aftertreatment 1 Diesel Oxidation Catalyst Intake Temperature Sensor – Data Not Rational – Drifted Low

Overview

Circuit Description

The aftertreatment exhaust gas temperature sensor module is a smart device that communicates with the engine control module via the J1939 data link. The aftertreatment exhaust gas temperature sensor module performs its own internal diagnostics and reports malfunctions back to the engine control module using the J1939 data link. The aftertreatment exhaust gas temperature sensor module is used to measure the aftertreatment diesel oxidation catalyst intake temperature, aftertreatment diesel particulate filter intake temperature, aftertreatment diesel particulate filter outlet temperature, and aftertreatment SCR outlet temperature. The temperature probes are permanently attached to the aftertreatment exhaust gas temperature sensor module and can not be replaced individually.

Component Location

The aftertreatment diesel oxidation catalyst intake temperature sensor is located in the aftertreatment system. It is located at the intake of the aftertreatment catalyst. Refer to the OEM service manual.

Conditions for Running the Diagnostics

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

Conditions for Setting the Fault Codes

The Engine Control Module (ECM) detected the temperature at the diesel oxidation catalyst intake was less than a calibrated threshold.

Action Taken When the Fault Code is Active

• The ECM illuminates the amber CHECK ENGINE lamp and/or malfunction indicator lamp (MIL) after the diagnostic fails on two consecutive trips.
• A default value for the aftertreatment diesel oxidation catalyst intake temperature sensor reading is used.
• Diesel exhaust fluid injection into the aftertreatment system is 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:

A malfunctioning aftertreatment diesel particulate filter intake temperature sensor

A malfunctioning aftertreatment diesel oxidation catalyst intake temperature 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.