What does code P249D mean?

DTC codes / P24xx · Auxiliary emission controls / P249D

P249DClosed Loop Reductant Injection Control At Limit Flow Too Low

P249D indicates that the engine control module (ECM) has commanded the reductant injection system into closed-loop control, but the actual flow rate remains below the minimum threshold despite the command being at its maximum limit. The computer is asking the diesel exhaust fluid (DEF) injector to spray as much as it can, yet the measured flow is still too low, so the system cannot meet the required emissions reduction.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaAuxiliary emission controls

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.