Volvo All Engines (2010 Emissions) Fault Code: SPN 4376 FMI 4 PID: PSID 105 Aftertreatment Diesel Exhaust Fluid Pump (DEF) Return Valve

When ignition key is turned to OFF position the selective catalytic reduction (SCR) system enters afterrun mode. During afterrun, system attempts to drain diesel exhaust fluid (DEF) from the DEF dosing valve, DEF pump and DEF lines. Aftertreatment control module (ACM) activates DEF return valve by grounding the control wire (-). When the return valve is activated, the DEF reverses flow back to the tank, and DEF dosing pressure is expected to drop. If the dosing pressure does not drop or if it increases during afterrun, the return valve is considered to have a mechanical fault.

Conditions for diagnostic trouble code (DTC):
1) The voltage at pin A137:12 is below normal value

Observable symptoms
1) Aftertreatment Diesel Exhaust Fluid (DEF) Pump After-run not possible

Probable cause
1) Short circuit to ground, Control wire (-)
2) Short circuit to ground, Common voltage supply
3) Wiring harness
4) Aftertreatment Diesel Exhaust Fluid (DEF) Pump