Stuck-open or leaking reductant injector, allowing continuous DEF flow; Faulty reductant pressure sensor reporting higher-than-actual pressure; Restricted or kinked reductant return line, causing pressure to build; Malfunctioning reductant pump or control module unable to regulate flow; Corroded, chafed, or shorted wiring in the reductant injector circuit; Internal leakage in the reductant dosing module or valve body; ECM software calibration issue or internal driver fault (less common)

DTC codes / P24xx · Auxiliary emission controls / P249E

P249EClosed Loop Reductant Injection Control At Limit Flow Too High

P249E indicates that the engine control module (ECM) has commanded the reductant injection system into closed-loop control, but the actual flow rate has exceeded the maximum limit the ECM can compensate for. The computer is trying to reduce diesel exhaust fluid (DEF) flow to match its target, but the flow remains too high even at the minimum command, so it sets this code.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyProfessional

AreaAuxiliary emission controls

Symptoms you may notice

Malfunction indicator lamp (MIL) illuminated, often with no other noticeable symptoms
Reductant low or system fault message displayed on the dashboard
Possible reduced engine power or limp mode if the fault persists
Exhaust aftertreatment system warning, such as a DEF quality or SCR efficiency message
Slightly increased DEF consumption noticed between fill-ups
In rare cases, a sulfur or ammonia odor from the exhaust

Common causes, most likely first

Stuck-open or leaking reductant injector, allowing continuous DEF flow
Faulty reductant pressure sensor reporting higher-than-actual pressure
Restricted or kinked reductant return line, causing pressure to build
Malfunctioning reductant pump or control module unable to regulate flow
Corroded, chafed, or shorted wiring in the reductant injector circuit
Internal leakage in the reductant dosing module or valve body
ECM software calibration issue or internal driver fault (less common)

How to diagnose and fix it

Scan all modules for stored and pending codes, and record freeze-frame data for P249E
Inspect the reductant injector and its wiring for visible leaks, corrosion, or damage
Check reductant pressure sensor readings against a mechanical gauge to verify accuracy
Perform an actuator test on the reductant injector and pump to observe flow behavior
Inspect the reductant return line for restrictions, kinks, or blockages
Replace the faulty reductant injector or pressure sensor as indicated by tests
Clear codes and perform a relearn or adaptation drive cycle, then verify the repair

What Most Techs Miss on P249E

A pressure sensor that reads high can mimic a stuck-open injector, so always verify sensor output with a mechanical gauge before replacing the injector.
The code can set from a restricted return line rather than an injector fault, especially if the vehicle has been run with contaminated or crystallized DEF.
In cold climates, frozen or slushy DEF can cause temporary high-flow readings that set P249E without any hard part failure.
Some vehicles require a reductant system adaptation reset after injector replacement; skipping this step can cause the code to return immediately.
P249E is often accompanied by SCR efficiency codes, but the root cause may be in the dosing control rather than the catalyst itself.

Can I keep driving with P249E?

You can usually drive the vehicle short distances to a repair shop, but avoid heavy loads and long trips because continued high DEF flow can damage the SCR catalyst and lead to derate. If the engine enters limp mode, stop driving and seek service.

Tools that help

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