NOTE: If codes 4077-0 or 3480-1 active, fix those first.

PROBABLE CAUSES:
1. Inspect entire exhaust system for leaks.
2. Inspect all 3 temperature sensors on the DPF/DOC system.
3. Inspect fuel line from doser block assy to the doser injection valve for kinks.
4. Remove the doser injection valve and coolant block from turbo outlet and inspect for carbon buildup. If present, replace the doser injector valve.
5. Clean the doser fuel lines.
6. Perform stationary regen.
7. Replace the HC doser block assy.