Overview
This code points to a problem in the DEF dosing system (aftertreatment). When dosing is not working correctly, the ECM may reduce power to protect emissions equipment.
What to check first
- Visual inspection of connectors and harness (rub points, corrosion)
- DEF quality and contamination
- Dosing valve operation (sticking/clogging)
Common fixes
- Repair wiring/connector damage
- Clean or replace the dosing valve
- Refill fresh DEF if contamination is suspected
Notes
Always confirm the exact SPN/FMI meaning for your engine/ECM calibration before replacing parts.