Cummins X12 CM2350 Fault Code 6799 |SPN 4334 |FMI 2/20

FAULT CODE 6799

Aftertreatment 1 Diesel Exhaust Fluid Pressure Sensor – Data Not Rational – Drifted High

Overview

Circuit Description

The Engine Control Module (ECM) provides a 5 volt supply and a ground to the aftertreatment diesel exhaust fluid pressure sensor. The pressure sensor provides a signal to the ECM on the sensor signal circuit. This sensor signal voltage changes, based on the aftertreatment diesel exhaust fluid pressure supplied by the dosing unit. The ECM will detect a low signal voltage at low diesel exhaust fluid pressures, and a high signal voltage at high diesel exhaust fluid pressures.

Component Location

The aftertreatment diesel exhaust fluid pressure sensor is internal to the aftertreatment diesel exhaust fluid dosing unit and can not be serviced separately.

Conditions for Running the Diagnostics

This diagnostic runs when diesel exhaust fluid dosing unit is fully primed, and is actively maintaining diesel exhaust fluid pressure in the dosing system.

Conditions for Setting the Fault Codes

The diesel exhaust fluid dosing unit was unable to maintain the commanded diesel exhaust fluid pressure.

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.
• 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 the “Aftertreatment Diesel Exhaust Fluid Doser Pump Override Test” found under “ECM Diagnostic Tests” in the INSITE electronic service tool
• 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:

• Leaking diesel exhaust fluid lines
• Malfunctioning or damaged diesel exhaust fluid dosing unit.
• Blocked or restricted diesel exhaust fluid dosing unit supply line fitting
• Blocked or restricted diesel exhaust fluid filters
• Malfunctioning diesel exhaust fluid pressure 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.