Reasons for Low Urea Pump Pressure in Mercedes-Benz GL350

1 Answers
NadiaLee
07/30/25 9:02am
Cause Analysis: Before urea injection, the urea pump builds up the urea pressure to 9bar, which is monitored by the pressure sensor inside the urea pump. After the engine starts, if the urea pump repeatedly attempts to build pressure but still fails to reach 9bar, this fault will be reported. The common causes of this fault include insufficient urea level, reversed urea pipeline, blocked or leaking suction pipe, pressure pipe leakage, etc. In rare cases, it may be due to a urea pump failure. Solutions and Steps: 1) Check if the urea level is sufficient; 2) Check if the urea pipeline is incorrectly connected or reversed; 3) Check if the suction pipe is bent or blocked; 4) Check for any signs of leakage in the suction pipe or pressure pipe; 5) If no issues are found above, inspect the urea pump interface for obvious blockages; 6) After replacing the urea pump, the fault is resolved, and normal urea pressure is built. Conclusion: Generally, incorrect connection, blockage, or leakage of the urea pipeline can easily cause this fault. However, in this case, the fault was due to a mechanical failure inside the urea pump, which prevented it from properly sucking urea, leading to pressure build-up failure.
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