Faulty Reductant Level Sensor
Reductant Level Sensor harness is open or shorted
Reductant Level Sensor circuit poor electrical connection
Engine Light ON (or Service Engine Soon Warning Light)
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 an integrated level sensor, pressure sensor, and fluid quality sensor, an injector fitted to the exhaust system, a fluid heater, and the catalyst.
The system is closely monitored for correct operation as a failure of the system will have a large impact on vehicle exhaust gas emissions of oxides of Nitrogen.