Volvo All Engines (2013 Emissions) Fault Code: P204F93 PID: EMS SCR System Performance Dosing Failure

Circuit description
When the aftertreatment selective catalytic reduction (SCR) system operates under normal conditions, the aftertreatment control module (ACM) monitors diesel exhaust fluid (DEF) dosing valve duty cycle and DEF pump control value. When the DEF dosing valve duty cycle increases above allowed threshold and the DEF pump control value decreases below expected threshold, the ACM stops DEF dosing and reports a fault. Only certain mechanical failure or blockage in the DEF dosing valve or DEF supply line from the DEF tank will result with this fault, it is not a indication of an electrical fault.

Conditions for diagnostic trouble code (DTC)
Clogged or damaged component

Observable symptoms
No aftertreatment diesel exhaust fluid (DEF) dosage
Engine de-rated

Probable cause
1) Aftertreatment diesel exhaust fluid (DEF) dosage valve