Volvo D13 SCR Derate - SPN 5394 FMI 5 Aftertreatment DEF Dosing Valve Fault

Question

My 2018 VNL 760 just went into 5 MPH derate while hauling through Nebraska. The dash is showing a DEF system failure and it won't let me initiate a parked regen at all. The pump sounds like it's priming but the dosing valve doesn't seem to be clicking.

Pete Sanders · Accepted Answer

Found the issue—the wiring harness had rubbed through against the frame rail about 6 inches back from the doser connector. I repaired the broken purple signal wire and replaced the Volvo DEF Dosing Valve (Part #22391563) because the internal solenoid was also testing high on resistance. After clearing the codes with Tech Tool and running a 'SCR System Crystalization Test' to reset the derate timers, the truck is back to full power. Total cost was about $550 for the part and 2 hours of labor.

Jake Morrison · Answer

FMI 5 usually points to an open circuit. You should check the wiring harness connector at the dosing injector on top of the decomposition pipe, as those wires often vibrate and break inside the insulation right at the plug.

wrenchqueen · Answer

If you have a multimeter, unplug the doser and check for resistance across the pins. It should be around 12-18 ohms. If it's infinity, the solenoid inside the injector is dead.

Marcus Bell · Answer

Check your DEF line heater fuses too. Sometimes a short in the heater line can cause weird communication faults with the SCR controller, though usually you'd see a different SPN for that.

Volvo D13 SCR Derate - SPN 5394 FMI 5 Aftertreatment DEF Dosing Valve Fault

Suggest a repair