Closed Loop Reductant Injection Control At Limit – Flow Too High
Table of contents
P249E MERCEDES-BENZ Possible Causes
- Exhaust Leaks
- Fuel contamination
- Faulty Diesel Particulate Filter (DPF)
- Faulty NOx Sensor
- Diesel Exhaust Fluid
- Faulty Selective Catalyst Reduction (SCR) Catalyst
How do I fix code P249E MERCEDES-BENZ?
Check the “Possible Causes” listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector’s pins.
Cost of diagnosing the P249E MERCEDES-BENZ code
The cost of diagnosing the P249E MERCEDES-BENZ code is 1.0 hour of labor. The auto repair labor rates vary by location, your vehicle’s make and model, and even your engine type. Most auto repairs shops charge between $75 and $150 per hour.
Possible Symptoms
- Engine Light ON (or Service Engine Soon Warning Light)
P249E MERCEDES-BENZ Description
Some manufacturers are now using a Diesel Exhaust Fluid (DEF) system commonly called a Selective Catalytic Reduction (SCR) system to reduce harmful Oxides of Nitrogen (NOx). The diesel exhaust fluid is a Urea based solution of approximately 32% Urea and 64% distilled water. The solution is injected into the exhaust gas stream upstream of the SCR catalyst. Once in the exhaust system it decomposes and becomes Ammonia (NH3) and Carbon dioxide (CO2). Within the catalyst, the NH3 and CO2 react with the Nox to create Oxygen (O2) and harmless Nitrogen (N2).
The system requires a storage tank for the diesel exhaust fluid, a pump with integrated level sensor, pressure sensor and fluid quality sensor, an injector fitted to the exhaust system, fluid heater and the catalyst. Sensors can also be fitted close to the SCR catalyst to monitor temperature during regeneration.
The system is closely monitored for correct operation as failure of the system will have a large impact on vehicle exhaust gas emissions of oxides of Nitrogen.