Two days ago, a card friend consulted in the evening that his liberation J6 sometimes limited the power of the engine due to the blockage of the urea nozzle. He removed the urea injection unit and cleaned it up. As a result, he found that the alarm light for insufficient coolant level was on. So why?
Due to the characteristics of urea solution, it means that when the temperature is low in winter, the urea solution is easy to crystallize or freeze. Once crystallized, it is easy to lead to the blockage of urea injection unit, resulting in the failure of SCR post-treatment system, and the power and torque output of the vehicle is limited. Therefore, generally, the vehicle SCR system is equipped with a heating system. The common heating methods generally use electric heating and coolant heating.
At present, SCR post-treatment system heated by coolant is relatively common. It may be known that there is a water heating system in the urea tank. When the temperature of the urea tank is lower than a certain temperature, When the coolant is higher than a certain temperature (e.g. 55 ℃), ECU opens the solenoid valve, and the hot coolant flows into the heating water pipe on the urea level and temperature sensor to heat the urea tank. The urea temperature sensor measures the urea temperature in the urea tank to control the starting and heating time of urea heating and thawing.
With the full implementation of the national four regulations and the promotion of the Yellow standard vehicle policy, more and more users will begin to use the national four medium heavy truck products with SCR system. In addition, the weather in the north is getting colder, the SCR system also needs to attract enough attention and conduct more preventive inspections.