Resolve the fault of the urea dosing pump

Oxidation catalyst, referred to as DOC. Its main function is to reduce carbon monoxide and hydrocarbons in engine emissions. Its main part is the oxidation catalyst. Compared with the other two technical routes, this technical route has fewer parts, simple assembly and lower cost.

Vehicle is weak, urea consumption is normal

1. Common phenomenon: The car owner reacts that the vehicle is weak, the urea consumption is normal, and the muffler can be found to emit a small amount of white smoke when refueling.

2. Analysis: Use the diagnostic instrument to read the fault code as the engine emission exceeds the standard, and there is no other fault. Remove the urea nozzle and use the diagnostic instrument to do the injection test, and no abnormality was found. During the inspection, it was found that a large number of urea crystals in the high-temperature catalytic tube were seriously blocked, so the exhaust elbow was removed to clean it and the air belt was used to clean the soot attached to the ceramic surface of the catalytic converter. After replacing the urea solution, the test failure disappeared.

3. Summary: After the failure of urea crystallization, a large amount of urea is accumulated 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 torque is limited after several driving cycles. The main reason is that the quality of urea is not up to standard.

The urea pressure is too low and the urea consumption is high

1. Common phenomenon: the instrument fault light in the car flashes frequently, and the fault code shows that the urea pressure is too low and the urea consumption is high.

2. Analysis: The upper part of the urea tank of the car has serious leakage. The urea tank assembly and the urea pump have been replaced. After the replacement, there is still a leakage of urea solution. During the inspection, it was found that the leaking position was the vent hole of the urea tank. To rule out the possibility of adding too much urea solution, check the water heating valve of the urea tank. It is found that the water heating valve is often damaged, replace the water heating valve, and troubleshoot.

3. Summary: The temperature in the urea tank is too high, causing the urea to volatilize and crystallize around the urea tank after being discharged from the vent hole. Excessive crystallization of the vent hole leads to blockage of the vent hole, and the urea pressure buildup is blocked, so the fault that the urea pressure is too low is reported.

Insufficient power, high or low urea consumption

1. Phenomenon: The fault light is always on. Underpowered, torque is limited to 1800 rpm. The SCR system is not working properly, the urea consumption is too high or too low.

2. Analysis: Use the diagnostic instrument to read the fault code: the voltage signal of the urea pump pressure sensor 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 inspection and processing of the urea pump power supply module, it was found that there was a large range of corrosion, which led to the connection of the plug-in wiring harness in the power supply module, and the wrong voltage value signal was transmitted to the ECU.

3. Summary: Replace the urea pump and the power supply module plug. Check again after the replacement, the urea fault code can be cleared, only the sensor power supply 3 cannot be cleared. Analyzing the sensor power supply 3 refers to the internal power supply module of the ECU, replacing the rail pressure sensor, and troubleshooting.