Common system faults and troubleshooting methods for SCR Aftertreatment System

1.NOx sensor malfunction and troubleshooting methods

Fault phenomenon: The fault light is on and the diagnostic instrument displays NOx. Sensor malfunction.

Troubleshooting: Check for NOx. Whether the sensor is heated: After powering on, gently touch the sensor. If there is no heating, check if the 24V power supply is normal. If there is no voltage, check if the circuit is short circuited or open circuited: If there is voltage, it may be a sensor malfunction and needs to be replaced. Check if the wiring connected to the NOx sensor is normal. If the fault is still not resolved, replace the NOx sensor. If the fault is resolved, confirm that the NOx sensor is faulty.

2.Malfunctions and troubleshooting methods of exhaust temperature sensor

Fault phenomenon: The fault light is on, and the diagnostic instrument shows that the exhaust temperature sensor is faulty.

Troubleshooting: Check the exhaust temperature sensor: Measure the resistance of the two pins of the exhaust temperature sensor and compare it with the temperature resistance meter of the exhaust temperature sensor. If it exceeds the range, the exhaust temperature sensor is faulty and needs to be replaced. Check the wiring harness: Measure whether there is 5V voltage at the end of the wiring harness. If not, check whether there is a short circuit or open circuit in the wiring harness.

3.Malfunctions and troubleshooting methods of metering pumps

Fault phenomenon: The fault light is on, and the diagnostic instrument displays a malfunction in the metering pump.
Troubleshooting: Check if the return pipe of the metering pump is blocked: Pull out the return pipe, start the engine and observe if there is any return. If there is no return, check if the return pipe is blocked. Remove the pipette and check if there is suction at the suction port of the pump. If it is a new pump or a pump that has been out of service for a long time, water can be injected into the suction port and the pump can be run until liquid is sprayed out from the return port, and check if there is any return liquid.

Check the compressed air pressure: After several cycles of liquid inlet and outlet, check if there is compressed air spraying from the injection port. If not, please check if there is any leakage in the compressed air management or if the compressed air pressure is sufficient (600 kPa~1200 kPa). If it still cannot be ruled out, replace the metering pump for testing. If the fault is resolved, it is determined to be an internal malfunction of the metering pump.