Powertrain, generic (extended)

P249D Closed Loop Reductant Injection Control At Limit - Flow Too Low

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

With P249D the NOx feedback loop of the SCR system has pushed its long-term correction as far as it may go because the delivered amount of DEF appears too small for the measured NOx. GM's tables judge this via the long-term adaptation value: above 1.69 in the 2014 diesel table and above 1.99 in the 2018 table; both rate it Type B, lamp after the second failing trip. Ford's 2023 diesel summary sets the code when the correction factor sits at its clip for 30 s while the SCR is warm and steady. Typical background is a partly blocked or worn dosing valve, weak pump pressure, crystallised urea or diluted fluid. The mirror code P249E means the loop had to take dosing back to its lower limit. Higher NOx output and possible later power reduction are the practical effects.

Likely causes

Dosing valve partly blocked by urea crystals or deposits
Weak DEF pump or restricted supply line and filter
Diluted or wrong fluid in the DEF tank
NOx sensor reading too high and misleading the controller

Symptoms

  • Malfunction indicator lamp on
  • Increased DEF warnings or later speed or power limitation
  • SCR efficiency code may follow

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€100–900
Time1–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

reductant injectorreductant pump

Related codes

P249EP249CP20EEP202E

References: gsi.ext.gm.com, gsi.ext.gm.com, fordservicecontent.com.