The AdBlue system is the core of post-emission treatment for diesel vehicles. It precisely injects urea solution into the exhaust pipe to convert harmful nitrogen oxides into harmless gases. The system consists of a storage tank, metering pump, injector, and multiple sensors. It relies on the close cooperation of mechanical and electronic control. Any abnormality in any part can affect emission control and may trigger engine torque limitation.

Common Faults and Their Causes

Urea crystallization: The solution dries and deposits at the nozzle, pipe, or valve, often caused by short-distance driving, premature engine shutdown, or long-idle periods. The crystallization can clog the injector, resulting in insufficient flow and dosage deviation.

Pressure pump failure: Wear of seals, blockage of filters, or air intake in the pipeline can prevent the pump from supplying liquid stably, manifested as dosage fluctuations, decreased SCR efficiency, and in severe cases, the system will force the pump to stop.

Sensor and dosage errors: Contamination of temperature, level, or nitrogen-oxygen sensors, calibration drift, or poor connection can transmit incorrect signals to the ECU, causing excessive or insufficient injection, and affecting the purification effect.

Low-temperature freezing: AdBlue freezes at around -11℃, and the expansion may crack the storage tank, hose, or injector. Even after thawing, the internal stress will reduce long-term reliability.

Diagnostic Methods

Read OBD fault codes: Can quickly locate pressure abnormalities, injection errors, or sensor failures.

Visual inspection: Observe crystallization at joints, pump body leakage, hose damage, or abnormal spray morphology, which can detect physical hazards in advance.

Preventive Maintenance Strategies

Regularly replace filters, clean nozzles to prevent impurities from clogging; calibrate sensors and pump pressure every certain operating period.

Before winter in cold regions, it is necessary to test the heating elements of the storage tank to avoid cracking.

Strictly control the quality of AdBlue: Must use solutions that meet ISO 22241 standards. Inferior products will exacerbate crystallization and injector wear.

Standard storage: Seal and protect from light to prevent contamination by moisture or dust.

Develop a routine inspection checklist (including pressure tests, electrical connections, pipe sealing), and integrate diagnostics into daily maintenance.

Conclusión

Most AdBlue faults are progressive. Early manifestations (such as occasional alarms, slight increase in fuel consumption) are often overlooked. By combining OBD diagnosis, regular cleaning, quality liquid supply, and seasonal protection, the risk of sudden failure can be significantly reduced. Simple daily maintenance is much more economical than replacing injectors or pump bodies and is also the key to ensuring long-term compliance with emission standards and vehicle power performance. Systematic maintenance can effectively extend equipment life and reduce unplanned downtime.