PACCAR PX-9 CM2350 (2013-17) Fault Code:1678 PID: SPN:3362 FMI:31 Aftertreatment Diesel Exhaust Fluid Dosing Unit Input Lines - Condition Exists - EcuForce Truck (2024)

Reason:
Aftertreatment Diesel Exhaust Fluid Dosing Unit Input Lines – Condition Exists. The aftertreatment diesel exhaust fluid dosing unit is unable to prime.

Effect:
Possible reduced engine performance

Circuit Description:
The diesel exhaust fluid dosing unit lines are responsible for transporting diesel exhaust fluid between the dosing unit, dosing valve, and diesel exhaust fluid tank.

Component Location:
There are three diesel exhaust fluid lines. One line is between the dosing unit and dosing valve, and the other two lines are between the dosing unit and the diesel exhaust fluid tank. These lines can be partially hidden from view by the SCR system and other vehicle components. Line routing will vary, based on the aftertreatment architecture and the OEM.

Conditions for Running the Diagnostics:
This diagnostic runs when the SCR system is trying to prime.

Conditions for Setting the Fault Codes:
The aftertreatment diesel exhaust fluid dosing unit was unable to successfully prime after multiple attempts.

Action Taken When the Fault Code is Active:
1) The ECM illuminates the amber CHECK ENGINE lamp and/or the Malfunction Indicator Lamp (MIL) immediately when the diagnostic runs and fails.
2) Engine torque will be severely reduced.

Vehicle speed will be limited to 8 km [5 mi] per hour after extended engine operation with the fault code active.

Conditions for Clearing the Fault Code:
1) To validate the repair, perform the “Aftertreatment Diesel Exhaust Fluid System Leak Test” found under “ECM Diagnostic Tests” in the INSITE™ electronic service tool
2) The fault code status displayed by INSITE™ electronic service tool will change to INACTIVE immediately after the diagnostic runs and passes.
3) The ECM will turn off the amber CHECK ENGINE lamp immediately after the diagnostic runs and passes.
4) 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.
5) The Reset All Faults command in INSITE™ electronic service tool can be used to clear active and inactive faults, as well as extinguish the MIL for OBD applications.

Shop Talk:
N/A

Possible Causes:
1) Low aftertreatment diesel exhaust fluid level in the diesel exhaust fluid tank
2) The line heaters are not successfully thawing the frozen diesel exhaust fluid
3) The diesel exhaust fluid pressure line between the dosing unit and dosing valve is kinked, broken, or disconnected
4) The diesel exhaust fluid suction line between the diesel exhaust fluid tank and the dosing unit is kinked, broken, or disconnected
5) Malfunctioning diesel exhaust fluid dosing unit
6) The diesel exhaust fluid suction and return lines between the dosing unit and diesel exhaust fluid tank are reversed
7) Debris from the diesel exhaust fluid tank. If debris is found in the diesel exhaust fluid tank, clean the diesel exhaust fluid tank thoroughly and fill with certified diesel exhaust fluid.

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