Code
P249E
Generic
P — Powertrain
Closed Loop Reductant Injection Control At Limit - Flow Too High
Views:
UK: 17
EN: 58
RU: 23
AI status
Completed
Completed
100%
Causes
- Stuck‑open or leaking reductant injector/nozzle
- Failed or overdriven reductant metering pump or pump relief valve
- Faulty reductant flow sensor or pressure sensor (incorrect reading)
- Contaminated or wrong reductant fluid (wrong concentration, particulates)
- Wiring short or driver fault causing excessive injector/pump duty or current
- Failed check valve or return line leak allowing uncontrolled flow
Symptoms
- Malfunction Indicator Lamp (MIL) illuminated with P249E stored
- Higher than normal reductant (DEF) consumption
- Reduced system performance or limp mode in some vehicles
- Visible leaks or dripping from injector or lines
- Strong ammonia/urea odor near SCR components
- Erratic or inconsistent reductant dosing values in live data
What to check
- Read and record all stored codes and freeze‑frame data
- Inspect DEF tank, lines, injector/nozzle and connectors for leaks, damage or contamination
- Verify DEF quality (concentration and contamination) with a refractometer or lab test
- Pull live data: commanded reductant rate vs. measured/actual flow, injector duty cycle, injector current, pump speed and pressure
- Check for additional ECM/communication errors and recent calibrations/updates
- Visually inspect wiring and connectors for corrosion, damage, or pin corrosion at injector, pump, and flow sensor
Signal parameters
- Commanded reductant injection rate (mg/stroke or g/s)
- Actual/measured reductant flow rate (g/min or ml/min)
- Injector duty cycle (%) and injector current (A)
- Metering pump speed (RPM) and pump current (A)
- Reductant pressure upstream/downstream of injector (bar/psi)
- DEF tank temperature and level
Diagnostic algorithm
- Retrieve DTCs and freeze frame; document operating conditions when fault occurred.
- Visually inspect DEF tank, lines, fittings, injector, and SCR components for leaks, damage, or contamination; repair obvious leaks.
- Verify DEF quality and concentration; if contaminated or wrong fluid, drain and refill with correct DEF and retest.
- With scan tool monitoring live data: command known injection pulses (if allowed) and compare commanded vs actual flow and injector duty/current.
- If measured flow remains higher than commanded, isolate the injector: disconnect injector/pump driver and observe if flow stops (controlled/secured per manufacturer procedures).
- Check flow/pressure sensor signals with multimeter/oscilloscope and compare to expected values; substitute known‑good sensor if available.
- Measure injector resistance and inspect nozzle for signs of leakage or wear; bench‑test or replace suspect injector(s).
- Inspect and test metering pump, relief valve and return circuit for internal leaks or stuck valves; replace pump or repair hydraulic components as needed.
- Inspect wiring harness and driver circuits for shorts/opens; repair connectors or wiring. Reflash ECM if a software/calibration issue is suspected.
- After repairs clear DTCs and perform verification drive/functional test to confirm closed‑loop reductant control returns to normal and no reoccurrence of P249E.
Likely causes
- Leaking reductant injector or failed nozzle (most common)
- Metering pump relief valve or pump mechanical failure
- Defective flow/pressure sensor reporting falsely low resistance or high flow
- Contaminated DEF (crystals/particles) causing incorrect spray/feedback
- Wiring/connector short to supply causing over‑actuation
Fault status
Status
P249E — Closed Loop Reductant Injection Control At Limit: measured reductant flow greater than commanded; closed‑loop control reached its limit and fault logged.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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