Current sensors belong to precision electronic components, and sometimes malfunctions are inevitable. Today, Weikewei Technology has summarized the following analysis of the causes of current sensor failures.

1. Damage phenomenon of intake pressure and temperature sensor:

① ON gear, the engine malfunction light is constantly on; ② When stepping on the accelerator slowly in place, a small amount of black smoke is emitted, and when accelerating rapidly, a large amount of black smoke is emitted; ③ The engine lacks power; ④ Fault code: P01D6 (intake pressure sensor voltage below lower limit) Cause analysis: Abnormal intake pressure signal, ECU cannot receive correct intake air quantity information, resulting in abnormal fuel injection quantity, insufficient combustion, engine fatigue, and black smoke during refueling. Problems with wiring harness connections and sensor failures can both cause this malfunction. Solution: Check the intake pressure and temperature sensor.

2. Damage phenomenon of water temperature sensor:

① ON gear, the engine malfunction light is constantly on; ② The maximum water temperature displayed in ON mode is always 120 ℃; ③ Engine torque limit and lack of power; ④ Fault code: P003D (water temperature sensor voltage below lower limit) Reason analysis: The water temperature sensor has failed. When the ECU detects that the output signal of the water temperature sensor is unreliable, a substitute value is used. The ECU limits the engine torque for the purpose of protecting the engine. Solution: Check the water temperature sensor.

3. Damage phenomenon of oil pressure sensor:

① After starting, the oil pressure indicator light stays on; ② The engine malfunction light is constantly on; ③ Idle speed, oil pressure value displayed as 0.99; ④ Fault code: P01CA (oil pressure sensor voltage above upper limit) Reason analysis: The oil pressure sensor probe is severely damaged, and the ECU detects that the oil pressure sensor is not connected. The instrument display value is an internal substitute value of the ECU. Solution: Check the oil pressure sensor.

4. Poor contact phenomenon of OBD socket terminals:

① In the ON position, the diagnostic tool is powered normally, but it cannot enter the ECU to read relevant information; ② No fault code. Cause analysis: The OBD socket terminal has exited, causing poor contact and preventing communication between the diagnostic instrument and ECU. Solution: Check the OBD socket terminals.

5. Short circuit phenomenon of nitrogen oxygen sensor wire harness:

① After startup, the OBD fault light remains on; ② Engine torque limit and lack of power; ③ Fault codes: P0050 (downstream nitrogen and oxygen sensor CAN signal reception timeout), P018C (downstream nitrogen and oxygen sensor preparation timeout). Cause analysis: The nitrogen oxygen sensor harness was worn out, short circuited to ground, and the nitrogen oxygen sensor could not work properly, resulting in excessive emissions, engine torque limit, and system alarm. Solution: Check the wiring harness of the nitrogen oxygen sensor.

6. Damage phenomenon of post-treatment heating relay box:

① After startup, the OBD fault light is on; ② Fault code: P028F (open circuit fault at the control end of the urea pressure pipeline heating relay). Cause analysis: Wiring harness open circuit fault. Solution: Check and repair the wiring harness of the heating relay box.

7. Fault phenomenon of open circuit in urea supply unit drive circuit:

① After startup, the OBD fault light remains on; ② Engine torque limit and lack of power; ③ Fault code: P3006 (urea supply unit drive circuit open circuit fault) ④ Failure to consume urea Reason analysis: The urea pump control line is open circuit, specifically manifested as the 10th pin of the urea pump electrical connector being falsely connected, the urea pump not working, the system cannot inject urea normally, resulting in excessive emissions, engine torque limit, and system alarm.

Solution: Check the wiring harness connector of the urea pump.

8. The phenomenon of instrument low-level software error not sending vehicle speed signal:

① When going uphill or accelerating rapidly, there will be a brief 1-2 second decrease in engine power; ② No fault code. Cause analysis: During the driving process, the vehicle speed signal sent by the instrument panel suddenly drops to 0, and the change in the vehicle speed signal causes the ECU to control the fuel volume, resulting in an instantaneous fuel cut-off phenomenon. Solution: If the instrument part number matched with the vehicle is 3820010-61B, please update to the latest version of the instrument with part number 3820010D61B.

9. SCR system urea reflux pipe blockage fault phenomenon:

① After startup, the OBD fault light remains on; ② Engine torque limit and lack of power; ③ Fault code: P0207 (SCR system urea reflux pipe blockage fault); ④ Not consuming urea. Cause analysis: Blockage of debris in the urea reflux pipe caused the system to be unable to inject urea normally, resulting in excessive emissions, engine torque limit, and system alarm. Solution: Check the urea reflux pipe (urea pipe between the urea pump and the urea tank).

10. Terminal misalignment of urea reflux heating pipeline connector:

① After startup, the OBD fault light remains on; ② Fault code: P0287 (open circuit or short circuit to ground fault in the circuit between the load end of the urea reflux line heating relay and the power supply). Cause analysis: After unplugging the urea heating reflux pipe connector, it was found that the terminal was inserted incorrectly. Solution: Repair the terminals and reinsert the connectors.

11. Symptoms of open circuit fault in urea pressure pipeline:

① After startup, the OBD fault light remains on; ② Fault code: P028E (open circuit or short circuit to ground fault in the circuit between the load end of the urea pressure pipeline heating relay and the power supply); ③ In winter, the engine may have limited torque and lack of power. Cause analysis: The heating wire of the urea pump pressure tube is broken, which prevents normal heating of urea in winter and causes the system to alarm. Solution: Check the pressure pipe of the urea pump (the urea pipeline from the urea pump to the urea nozzle).

12. Fault phenomenon of open circuit in urea suction pipeline:

① After startup, the OBD fault light remains on; ② Fault code: P029A (open circuit or short circuit to ground fault in the circuit between the load end of the urea intake pipeline heating relay and the power supply); ③ In winter, the engine may have limited torque and lack of power. Cause analysis: The heating wire of the urea pump suction pipe is broken, which prevents normal heating of urea in winter and causes the system to alarm. Solution: Check the suction pipe of the urea pump (the urea pipeline from the urea tank to the urea pump).

13. Fault phenomenon of open circuit in urea reflux pipeline:

① After startup, the OBD fault light remains on; ② Fault code: P0287 (open circuit or short circuit to ground fault in the circuit between the load end of the urea reflux pipeline heating relay and the power supply); ③ In winter, the engine may have limited torque and lack of power. Cause analysis: The heating wire of the urea pump reflux pipe is broken, which prevents normal heating of urea in winter and causes the system to alarm.

Solution: Check the urea pump return pipe (the urea pipeline from the urea pump to the urea tank).

14. Leakage of urea at the electrical connector position of the urea pump:

① After startup, the OBD fault light is on; ② Engine torque limit and lack of power; ③ Not consuming urea; ④ Fault codes: P0227, P0228, P01FC, P01FB, P02B1, P02A1, P01FA, P01FB (please refer to the maintenance manual for corresponding information of fault codes). Cause analysis: Urea leaked from the electrical connector of the urea pump, corroding the metal pins and causing short circuit or open circuit faults in the circuit. (In severe cases, it may burn out the rail pressure sensor, which shares the same power supply with the internal pressure sensor of the urea pump in the ECU.) Solution: Check the electrical connectors of the urea pump and replace the damaged parts.

15. Open circuit phenomenon of exhaust temperature sensor harness:

① After startup, the OBD fault light is on; ② Engine torque limit and lack of power; ③ Not consuming urea; ④ Fault code: P027B (SCR catalyst upstream temperature sensor signal voltage too high fault). Cause analysis: The wiring harness of the exhaust temperature sensor was worn off, and the ECU was unable to obtain the upstream exhaust temperature of the SCR catalyst, resulting in the urea pump not building pressure and not consuming urea, leading to excessive emissions, engine torque limit, and system alarm. Solution: Repair the wiring harness and wrap it properly.

16. Reverse installation of crankshaft sensor and oil metering unit connector:

① The maximum speed is limited to 1800rpm; ② The startup time is too long; ③ Fault codes: P00EF (no signal from crankshaft sensor), P01E2 (pressure relief valve opened). Reason analysis: The crankshaft sensor and oil metering unit connectors are plugged in incorrectly, and neither can provide normal signals to the ECU. Solution: Swap the connectors of the crankshaft sensor and oil metering unit.

17. Regularly open phenomenon of urea tank antifreeze solenoid valve:

The temperature of the urea tank is high, and urea is discharged from the vent plug of the urea tank. Reason analysis: During the driving process, the urea tank antifreeze solenoid valve is always on, which means that the antifreeze keeps thawing the urea tank There are impurities in the coolant that accumulate near the diaphragm, causing them to squeeze and form pits on the diaphragm, which affects the sealing The working pressure range of the solenoid valve does not match the actual pressure value. The working pressure of the current solenoid valve is 20kPa to 250kPa, and the actual pipeline pressure may be lower than 20kPa. When it is lower than 20kPa, the diaphragm cannot be tightly pressed and cannot be effectively sealed.

Solution: Change the solenoid valve assembly to the latest version according to the parts catalog.

18. Excessive sensitivity of nitrogen and oxygen sensor concentration limit during engine bench calibration:

The export vehicle J6 from Russia (common rail system) has the highest frequency of false alarms from nitrogen and oxygen sensors, and similar problems also occur frequently in domestic common rail systems: ① After starting, the OBD fault light stays on; ② Engine torque limit and lack of power; ③ Fault code: P01FC: NOx peak check fault, P01FF: NOx incremental check fault. Reason analysis: The calibration of nitrogen oxide NOx concentration limit is unreasonable, and the threshold value is too sensitive. The peak calibration limit should be changed from 200ppm to 50ppm, and the signal variation range should be changed from 400ppm to 50ppm. Solution: Flashing the latest version of data.

19. Permanent fault phenomenon of motor speed deviation in urea supply unit:

① The OBD light is on, with no limit on twisting; ② Fault code: P02AB (permanent fault of urea supply unit motor speed deviation). Cause analysis: The urea pump motor is damaged. Solution: Replace BOSCH 2.2 urea pump 1161010-51B.

20. Crystallization phenomenon at the urea nozzle seat:

The urea nozzle seat is uniformly crystallized, and the middle spray hole is not blocked, allowing for ventilation.

Cause analysis: The urea nozzle seat has local swirling flow, causing a thin layer of urea crystals. Solution: This is a normal phenomenon and does not require treatment if it does not affect emissions.

21. Crystallization phenomenon at the inlet of the post processor:

There is uniform crystallization at the air inlet of the post-processing unit, without large chunks of crystalline urea.

Cause analysis: During use, a thin layer of urea crystals will form near the interface between the post-processing unit and the intake pipe. Solution: This is a normal phenomenon and does not require treatment if it does not affect emissions.

The above is a summary of the causes of current sensor failures by Weikewei Technology. If you want to learn more, please continue to follow Weikewei Technology. Recommended articles《How to choose high-precision current sensors》