The Aftertreatment Hydrocarbon Dosing Module contains three non serviceable valves, the Aftertreatment Fuel Shutoff Valve, Aftertreatment Purge Air Valve and Aftertreatment Hydrocarbon Dosing Valve, and a serviceable Aftertreatment Fuel Pressure Sensor.
During Air Purge operation the Engine Control Module (ECM) sends a voltage signal to activate the Aftertreatment Purge Air Valve open. This allows air pressure to flow into the Aftertreament Hydrocarbon Dosing Module. The ECM then sends a PWM signal to the Aftertreatment Hydrocarbon Dosing Valve that allows purge air pressure to be monitored by a signal from the Aftertreatment Fuel Pressure Sensor to the ECM.

Conditions for diagnostic trouble code (DTC):
1) Voltage above normal or shorted high
2) Diagnostic operating conditions
3) Output activated

Observable symptoms
1) Regeneration not possible

Probable cause
1) Connector
2) Engine wiring harness
3) Aftertreatment Hydrocarbon Dosing Module
4) Engine control module (ECM)