PACCAR PX-9 CM2350 (2013-17) Fault Code:3578 PID: SPN:4376 FMI:4 Aftertreatment Diesel Exhaust Fluid Return Valve – Voltage Below Normal or Shorted to Low Source

Reason:
Aftertreatment Diesel Exhaust Fluid Return Valve – Voltage Below Normal, or Shorted to Low Source. Low signal voltage detected at the diesel exhaust fluid return valve.

Effect:
Possible reduced engine performance.

Circuit Description:
The aftertreatment diesel exhaust fluid return valve is controlled by the Engine Control Module (ECM). The return valve position determines where diesel exhaust fluid will flow as it exits the dosing unit. When the return valve is activated, the dosing system will purge and return the diesel exhaust fluid in the lines to the tank.

Component Location:
The aftertreatment diesel exhaust fluid return valve is internal to the aftertreatment diesel exhaust fluid dosing unit and can not be serviced separately.

Conditions for Running the Diagnostics:
This diagnostic only runs when the aftertreatment diesel exhaust fluid dosing system is purging.

Conditions for Setting the Fault Codes:
The Engine Control Module (ECM) detected the aftertreatment diesel exhaust fluid return valve voltage was out of range low.

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) Diesel exhaust fluid injection into the aftertreatment system is disabled.
3) 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, perform a key cycle, start the engine and let it idle for 1 minute.
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:
If this fault is active, the dosing system may not be able to purge, which means there will be diesel exhaust fluid left in the lines. Care must be taken when removing connections. Also, lines could freeze and become damaged in cold weather if the system is not properly purged.

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.

Possible Causes:
1) Inactive fault codes
2) Damaged aftertreatment DEF return valve and electrical connections
3) Faulty ECM
4) Faulty OEM harness
5) Open circuit
6) Pin-to-pin short circuit