Urea sensor

The front part of the urea pressure sensor is used to detect the urea pressure, and the rear part is responsible for detecting the mixing pressure of urea and air in the mixing chamber. When the component fails: the urea consumption is abnormal, and the vehicle lights the fault light. When the fault code is the current fault, the engine performance is limited in speed and torque.

Inspection and maintenance parameters:

Use a multimeter to measure the open circuit voltage of the urea pressure sensor, turn on the key switch and unplug the key plug, and measure 5V (power), 0V (signal) and 0V (ground). To measure closed-circuit voltage, first turn on the key, plug in the plug and break the wire at the back to measure the voltage, measure 5V (power), 0.8-1V (signal) and 0V (ground).

Related fault codes:

Line inspection ideas:

1. Use a multimeter to measure the open-circuit voltage of the plug as 5V (power), 0V (signal), 0V (ground wire, the resistance to ground is less than 0.2Ω) if the normal line and the computer version are no problem.

2. The FC3571 fault is reported, which is generally a short circuit of the signal line to the power supply line, an open circuit of the ground wire or an internal fault of the component.

3. The FC3572 fault is reported, which is generally due to open circuit of the power supply line or signal line, short circuit to ground or internal damage of the component.

4. Report FC3573 faults, generally because the plug is loose, the virtual connection or the internal damage of the component

Performance check ideas:

1. Focus on checking whether the urea dosing pump plug has virtual connection, water ingress and corrosion.

2. When the urea pressure sensor reports high or low pressure, check whether the sensor sensing metal sheet is deformed or damaged and whether the sealing is damaged.

3. In order to prevent false alarms caused by abnormal urea pressure sensor, the components can be replaced for testing.

4. The FC4239 fault code is reported. Generally, the ECM monitors that the actual pressure is too high and reports a fault. The normal mixed pressure value should be between 330~430kpa when the urea dosing pump is ready to inject (pre-injection is successful) and the injection stage. If the ECM detects that the actual pressure is higher than 500kpa and continues for more than 8s, it will report a fault; or in the pre-injection stage, it will report a fault if it is higher than 150kpa and continue for 0.5s. possible reason:

①The nozzle is blocked, the injection pipe is bent and blocked;

②The urea crystals inside the urea pump are blocked;

③The compressed air pressure is too high;

④ Check whether the sensing metal sheet of the mixing chamber pressure sensor is damaged;

5. The FC4238 fault code is reported. Generally, the ECM monitors that the actual pressure is too low and reports a fault. The normal mixed pressure value should be between 330~430kpa when the urea dosing pump is ready to inject (pre-injection is successful) and the injection stage. possible reason:

①Insufficient compressed air pressure;

②The urea crystals inside the urea pump are blocked;

③ Check whether the sensor sensing metal sheet is damaged and whether the O-ring is damaged;

④The one-way valve of the gas path is damaged or the filter screen is blocked;

⑤ The injection valve leaks;

6. If the above measured values ​​are normal, consider flashing the data or replacing the computer board.