What Causes a Vehicle Not to Consume Urea?
3 Answers
It may be that the vehicle's SCR system is not functioning. Due to environmental protection agencies in various countries proposing further reductions in nitrogen oxide pollutants emitted by diesel engines, engine manufacturers have begun using SCR technology to meet the requirements of environmental agencies. The addition of urea in vehicles is intended to treat diesel engine exhaust. The working principle is as follows: when nitrogen oxides are detected in the exhaust pipe, the urea tank automatically sprays diesel exhaust fluid. The diesel exhaust fluid and nitrogen oxides undergo a redox reaction in the SCR catalytic reaction tank, producing non-polluting nitrogen and water vapor that are then emitted.
I've been driving a diesel car for several years and have seen this issue quite often. The main causes of abnormal urea consumption are varied. The most common is poor quality or expired urea—using inferior urea can cause the system to shut down automatically to protect the engine. Another issue is urea freezing at low temperatures, especially in winter when the pump and pipes freeze below zero, preventing urea injection. There could also be a malfunction in the urea pump or nozzle, either due to damage or clogging by debris, requiring professional cleaning. Additionally, faulty sensors like the NOx sensor might mistakenly indicate emissions compliance, failing to trigger urea injection. Driving habits also play a role—short trips may not allow the system to reach the required temperature for activation. My advice is to first check the urea tank level and refill with high-quality urea if low. If the problem persists, take the car to a repair shop immediately for a diagnostic scan to avoid penalties for exceeding emissions limits.
As a diesel enthusiast who frequents truck forums, I believe there could be several reasons why a vehicle isn't using urea. First, the urea itself might be depleted or diluted with water, causing the system to detect substandard quality and halt operation. Second, cold weather can cause freezing, especially during northern winters, so it's essential to ensure the heating system is functioning properly. Third, components like the pump or nozzle might be stuck or worn out, possibly due to long-term neglect of cleaning and maintenance. Fourth, there could be issues with the vehicle's computer settings, such as ECU malfunctions or software bugs causing the system to misjudge. Fifth, improper driving habits, like frequent short trips or low-speed driving in cold conditions, might prevent the urea system from activating. I once experienced a clogged nozzle myself, which was resolved after replacing the part. To prevent most issues, it's advisable to use reputable brand urea, avoid cheap alternatives, allow longer warm-up times in winter, and schedule regular check-ups at the shop.
