Cummins X15 CM2350 X116B Performance Series (2018 & Newer) Fault Code: 6781 PID: SPN: 4765 FMI: 2/21 Aftertreatment 1 Diesel Oxidation Catalyst Intake Temperature Sensor – Data Not Rational – Drifted Low

Lamp:
None

Reason:
An offset in the diesel oxidation catalyst Intake temperature sensor reading has been detected.

Effect:
Possible reduced engine performance.

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.

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 Code:
The Engine Control Module (ECM) detected the difference between the aftertreatment diesel oxidation catalyst intake temperature sensor data and diesel particulate filter intake temperature sensor data did not match the expected value for the present engine operating conditions.

Action Taken When the Fault Code is Active:
1. The ECM illuminates the amber check engine lamp and/or malfunction indicator lamp (MIL) after the diagnostic fails on two consecutive trips.
2. A default value for the aftertreatment diesel oxidation catalyst intake temperature sensor reading is used.
3. Diesel exhaust fluid injection into the aftertreatment system is disabled.
4. 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:
1. 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.
2. 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.
3. The fault code status displayed by the recommended diagnostic tool or equivalent will change to inactive immediately after the diagnostic runs and passes.
4. The ECM will turn off the amber check engine lamp immediately after the diagnostic runs and passes.
5. 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.
6. The “reset all faults” command in the recommended diagnostic tool or equivalent can be used to clear active and inactive faults, as well as extinguish the MIL for OBD applications.

Shop Talk:
1. Possible causes of this fault code include:
2. A malfunctioning aftertreatment diesel particulate filter intake temperature sensor.
3. A malfunctioning aftertreatment diesel oxidation catalyst intake temperature sensor.
4. Reference the appropriate OEM wiring diagram when troubleshooting circuits that utilize wiring supplied by the OEM.
5. 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.