1Vehicle weakness, normal urea consumption
Trouble phenomenon: The vehicle owner responded that the vehicle was weak and the urea consumption was normal, and the muffler could be found to emit a small amount of white smoke after refueling.
Fault analysis: read the fault code with the diagnostic instrument to indicate that the engine emissions exceed the standard, and there is no other fault. The urea nozzle was removed and the diagnostic instrument was used for the injection test, and no abnormality was found. During the inspection, a large number of urea crystals in the high-temperature catalyst tube were found to be seriously blocked, so the exhaust elbow was removed and the gas belt was used to clean the soot attached to the ceramic surface of the catalyst. The failure of the test run after replacing the urea solution disappeared.
Fault summary: After the urea crystallization fails, a large amount of urea accumulates in the exhaust pipe, which not only causes the engine exhaust to be blocked and weak, but also causes the emission to exceed the standard, and the OBD is limited to torque after a few driving cycles. The main reason is mostly that the quality of urea is not up to standard.
2 Urea pressure is too low and urea consumption is high
Trouble phenomenon: Frequent flashing of the instrument fault light in the car, the fault code shows that the urea pressure is too low and the urea consumption is high.
Failure analysis: The upper part of the urea tank of the vehicle leaked seriously. After replacing the urea tank assembly and urea pump, there was still leakage of urea solution after the replacement. During the inspection, it was found that the location of the leakage was the vent hole of the urea tank. Eliminate the possibility of adding too much urea solution and check the water heating valve of the urea tank. The water heating valve is found to be damaged. Replace the water heating valve and eliminate the fault.
Fault summary: The high temperature in the urea tank causes urea to volatilize, which will crystallize around the urea tank after being discharged from the vent. Excessive crystallization of the vent holes leads to blockage of the vent holes. When the urea system is working, the vacuum in the box is severe, and the pressure build-up of the urea is blocked, so the fault of the urea pressure being too low is reported.
3 Insufficient power, urea consumption is too high or too low
Fault phenomenon: the fault light is always on. The power is insufficient and the torque is limited to 1800 rpm. The SCR system is not working properly, and the urea consumption is too high or too low.
Fault analysis: Read the fault code with A60N diagnostic instrument. The voltage signal of the pressure sensor of the urea pump is high, the actuator 2 is short-circuited to the ground, the urea reversing valve actuator is open, and the sensor power supply 3 is wrong. After the inspection, the power supply module of the urea pump was processed, and it was found that there was a large range of corrosion, which caused the power supply module’s internal wiring harness to be connected to the power supply module and sent the wrong voltage signal to the ECU.
Solution: Replace the urea pump and the power supply module plug. After the replacement, the urea fault code can be cleared by detecting it again. Only the sensor power supply 3 cannot be cleared. Analysis of the sensor power supply 3 refers to the internal power supply module of the ECU, and troubleshooting when replacing the rail pressure sensor.