Volvo All Engines (2013 Emissions) Fault Code: P20C112 PID: ACM Reductant Heater “C” Control

Circuit description
This diagnostic trouble code (DTC) indicates a malfunction at the diesel exhaust fluid (DEF) line heater 3. The DEF lines and line connections between the DEF tank and DEF pump are electrically heated by the DEF line heater 3. The DEF line heater 3 is normally OFF and is commended ON by the aftertreatment control module (ACM) when the ambient air temperature (AAT) and DEF tank temperature are below calibrated threshold. The ACM controls the DEF heater 3 by supplying battery voltage to the common voltage supply circuit and grounding control wire (-) circuit using pulse width modulated signal.

Conditions for diagnostic trouble code (DTC)
The voltage at pin A137:24 is above normal value

Observable symptoms
Ammonia smell can occur if the aftertreatment diesel exhaust fluid (DEF) warmed too much

Probable cause
1) Connector
2) Wiring harness
3) Aftertreatment Diesel Exhaust Fluid (DEF) Line Heater 3