DEF System Purge Valve Malfunction

What this code means

The DEF system purge valve that drains DEF lines back to the tank during shutdown (to prevent freezing) has malfunctioned.

Symptoms

• DEF lines freeze in cold weather
• DEF system inoperative after cold soak
• Check Engine Light in cold conditions
• DEF pressure does not build on startup
• SCR system delayed activation in winter

Common causes

• Purge valve stuck open or closed
• Purge valve solenoid failure
• Wiring fault to purge valve
• Valve frozen in position
• Control circuit fault

Diagnostic steps

1. Test purge valve operation at shutdown
2. Command valve via scan tool
3. Check valve solenoid resistance
4. Inspect valve for ice or crystallization
5. Monitor DEF line pressure during purge cycle

Repair notes

Replace DEF purge valve. Ensure DEF line heaters function to prevent future freeze damage.

Other Powertrain codes on this vehicle