What Causes a Diesel Vehicle Not to Consume Urea?
2 Answers
It may be due to the SCR system not functioning properly. Here are the relevant explanations: 1. Working Principle: When nitrogen oxides are detected in the exhaust pipe, the urea tank automatically sprays diesel exhaust fluid (DEF). The DEF and nitrogen oxides undergo a redox reaction in the SCR catalytic converter, producing non-polluting nitrogen and water vapor that are then expelled. 2. Automotive Urea: The technical name is diesel exhaust fluid (DEF), used in diesel engines. There is an integrated chip control between the engine and the urea tank, which determines the amount of DEF to inject based on the engine's power output. Currently, if the system is clogged and unable to spray DEF, it will result in reduced engine power and performance.
I've seen plenty of diesel vehicles not using urea in my ten years as a mechanic. The most common issue is clogged urea pumps or injectors, especially in winter when urea crystals get stuck in the pipes, rendering the injection system practically paralyzed. Sensors also love causing trouble—when the concentration sensor or temperature probe fails, the ECU has no idea when to inject urea. There are even more outrageous cases where people modify their vehicles to bypass the urea system to save money, only to end up with black smoke from the exhaust and hefty environmental fines. Oh, and if the urea tank heater pipe leaks or burns out, frozen urea can completely disable the entire injection system. Lastly, don’t forget about ECU control module failures—system crashes or incorrect data flashing can shut it down entirely. My advice? Check urea quality monthly and avoid overfilling to prevent spillage and chassis corrosion.
