Aftertreatment Control Module (ACM) monitors DEF tank temperature and uses it to control the Aftertreatment DEF Tank Heater valve to keep the DEF from freezing.
This temperature monitoring is also used to avoid stopped DEF dosing due to high DEF tank temperatures. If the DEF temperature is too high, reverse flow will be activated, if the temperature stays high for a short duration, a DTC is set.

Conditions for diagnostic trouble code (DTC):
1) Short circuit to ground in the component or wiring
2) Short circuit to lower voltage

Observable symptoms
1) None

Probable cause
1) Connector
2) Wiring harness
3) Short circuit to ground, Signal wire
4) Aftertreatment diesel exhaust fluid (DEF) tank, Temperature Sensor