- Damage of intake pressure and temperature sensor:
① In ON gear, the engine fault light is always on; ② A small amount of black smoke is emitted when slowly stepping on the accelerator in place, and a large amount of black smoke is emitted when accelerating rapidly; ③ The engine is sluggish; ④ Fault code: P01D6 (intake pressure sensor voltage is lower than the lower limit) Cause analysis: the intake pressure signal is abnormal, and the ECU cannot receive the correct intake quantity information, resulting in the abnormal injection quantity, which means that the combustion is not sufficient, the engine is sluggish, and black smoke is emitted during the refueling process. A problem with the harness connection and a sensor failure can cause this fault. Solution: Check the intake pressure and temperature sensor.
- Damage of water temperature sensor:
① In ON gear, the engine fault light is always on; ② The maximum water temperature at ON position is always 120 ℃; ③ The engine is limited in torsion and lack of strength; ④ Fault code: P003D (water temperature sensor voltage is lower than the lower limit value) Cause analysis: the water temperature sensor fails. When the ECU detects that the output signal of the water temperature sensor is not credible, it uses the substitute value. The ECU limits the torque of the engine for the purpose of protecting the engine. Solution: Check the water temperature sensor.
- Oil pressure sensor damage:
① After starting, the oil pressure indicator is always on; ② The engine fault light is always on; ③ At idle speed, the oil pressure value is 0.99; ④ Fault code: P01CA (oil pressure sensor voltage is higher than the upper limit) Cause analysis: the oil pressure sensor probe is seriously damaged, the ECU detects that the oil pressure sensor is not connected, and the instrument display value is the replacement value inside the ECU. Solution: Check the oil pressure sensor.
- Poor contact of OBD socket terminal:
① In the ON position, the power supply of the diagnostic instrument is normal, but it cannot enter the ECU to read relevant information; ② No fault code. Cause analysis: The OBD socket terminal exited, resulting in poor contact, and the diagnostic instrument and ECU could not communicate. Solution: Check the OBD socket terminal.
- Short circuit phenomenon of nitrogen oxygen sensor wire harness: ① After starting, the OBD fault light is always on; ② The engine is limited in torsion and lack of strength; ③ Fault codes: P0050 (downstream nitrogen oxygen sensor CAN signal receiving timeout), P018C (downstream nitrogen oxygen sensor preparation timeout). Cause analysis: the harness of the nitrogen oxygen sensor is worn, short-circuited and grounded, and the nitrogen oxygen sensor cannot work normally, resulting in excessive emissions, engine torque limitation, and system alarm. Solution: Check the nitrogen oxygen sensor wire harness.
- Damage of after-treatment heating relay box:
① After starting, the OBD fault light is on; ② Fault code: P028F (open circuit fault at control end of heating relay of urea pressure pipeline). Cause analysis: harness open circuit fault. Solution: Check and repair the harness of heating relay box.
- Open circuit fault phenomenon of urea supply unit drive circuit:
① After starting, the OBD fault light is always on; ② The engine is limited in torsion and lack of strength; ③ Fault code: P3006 (open circuit fault of the drive circuit of the urea supply unit) ④ Analysis of the reason for not consuming urea: the control line of the urea pump is open circuit, which is specifically manifested by the virtual connection of the 10th pin of the electrical connector of the urea pump, the urea pump does not work, and the system cannot normally inject urea, resulting in excessive emissions, engine torque limit, and system alarm.
Solution: Check the connector at the harness end of the urea pump.
- Phenomenon that the bottom software of the instrument does not send the vehicle speed signal due to error:
① When going up the hill or accelerating rapidly, the power of the engine will drop for 1-2 seconds; ② No fault code. Cause analysis: during driving, the vehicle speed signal sent by the instrument suddenly drops to 0, and the change of vehicle speed signal causes the change of ECU control fuel quantity, resulting in the instantaneous fuel cut-off.
- The urea return pipe of SCR system is blocked
① After starting, the OBD fault light is always on; ② The engine is limited in torsion and lack of strength; ③ Fault code: P0207 (urea return pipe of SCR system is blocked); ④ No urea consumption. Cause analysis: sundries in the urea return pipe are blocked, causing the system to be unable to inject urea normally, resulting in excessive emissions, engine torque limitation and system alarm. Solution: Check the urea return pipe (the urea pipe between the urea pump and the urea tank).
- The connector terminal of the urea reflux heating pipeline is skewed:
① After starting, the OBD fault light is always on; ② Fault code: P0287 (open circuit or short circuit to ground fault in the circuit between the load end of the heating relay of the urea return line and the power supply). Cause analysis: after unplugging the connector of the urea heating return pipe, it was found that the terminal was accidentally inserted askew. Solution: repair the terminal and plug in the connector again.
- Open circuit fault of urea pressure pipeline:
① After starting, the OBD fault light is always on; ② Fault code: P028E (open circuit or short circuit to ground fault in the circuit between the load end of the heating relay of the urea pressure pipeline and the power supply); ③ In winter, the engine may be limited in torsion and lack of strength. Cause analysis: the heating wire of the pressure pipe of the urea pump is open circuit, which leads to the failure of heating the urea normally in winter, and the system alarms at the same time. Solution: Check the pressure pipe of the urea pump (the urea pipe from the urea pump to the urea nozzle).
- Open circuit fault of urea suction pipe:
① After starting, the OBD fault light is always on; ② Fault code: P029A (open circuit or short circuit to ground fault in the circuit between the load end of the heating relay of the urea suction pipeline and the power supply); ③ In winter, the engine may be limited in torsion and lack of strength. Cause analysis: the heating wire of the suction pipe of the urea pump is open circuit, which leads to the failure of heating the urea normally in winter, and the system alarms at the same time. Solution: Check the suction pipe of the urea pump (the urea pipeline from the urea tank to the urea pump).
- Open circuit fault of urea return line:
① After starting, the OBD fault light is always on; ② Fault code: P0287 (open circuit or short circuit to ground fault in the circuit between the load end of the heating relay of the urea return line and the power supply); ③ In winter, the engine may be limited in torsion and lack of strength. Cause analysis: the heating wire of the return pipe of the urea pump is open circuit, which causes that the urea can not be heated normally in winter, and the system alarms at the same time. Solution: Check the return pipe of the urea pump (the urea pipeline from the urea pump to the urea tank).
- Urea leakage at the electrical connector of the urea pump:
① After starting, the OBD fault light is on; ② The engine is limited in torsion and lack of strength; ③ No urea consumption; ④ Fault codes: P0227, P0228, P01FC, P01FB, P02B1, P02A1, P01FA, P01FB (refer to the maintenance manual for the corresponding information of fault codes). Cause analysis: urea leakage at the electrical connector of the urea pump corrodes the metal pin, resulting in short circuit and open circuit fault of the circuit. (In serious cases, the rail pressure sensor will be burned out. The rail pressure sensor and the internal pressure sensor of the urea pump share the same power supply inside the ECU.)
Solution: check the electrical connector of the urea pump and replace the damaged part.
- Open circuit of exhaust temperature sensor harness:
① After starting, the OBD fault light is on; ② The engine is limited in torsion and lack of strength; ③ No urea consumption; ④ Fault code: P027B (SCR catalyst upstream temperature sensor signal high voltage fault). Cause analysis: the exhaust temperature sensor harness was worn out, and the ECU could not obtain the exhaust temperature upstream of the SCR catalyst, causing the urea pump not to build pressure and not consume urea, resulting in excessive emissions, engine torque limitation, and system alarm. Solution: repair the harness and wrap it.
- The connector of crankshaft sensor and oil metering unit is installed reversely:
① The maximum speed is limited to 1800 rpm; ② The starting time is too long; ③ Fault code: P00EF (crankshaft sensor has no signal), P01E2 (pressure relief valve is opened). Cause analysis: crankshaft sensor and oil metering
The unit connector is inserted reversely and cannot provide normal signal to ECU. Solution: Align the connectors of crankshaft sensor and oil metering unit.
- The anti-freeze solenoid valve of the urea tank is normally open: the temperature of the urea tank is high, and urea is discharged from the vent plug of the urea tank. Cause analysis: During driving, the antifreeze solenoid valve of the urea tank is normally open, that is, the antifreeze has been thawing the urea tank. ① There are impurities in the coolant, which accumulate near the diaphragm, and the impurities squeeze the diaphragm to form pits, affecting the sealing; ② 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~250kPa, and the actual pipeline pressure may be lower than 20kPa. When the pressure is lower than 20kPa, the diaphragm cannot be compressed and effectively sealed).
Solution: Change the solenoid valve assembly to the latest version according to the parts catalog.
- The concentration limit of nitrogen and oxygen sensor in engine bench calibration is too sensitive:
Russia J6 export vehicle (common rail system) has the highest frequency of nitrogen and oxygen sensor misreporting faults, and domestic common rail system also has a large number of similar problems: ① after starting, the OBD fault light is always on; ② The engine is limited in torsion and lack of strength; ③ Fault code: P01FC: NOx peak check fault, P01FF: NOx increment check fault. Cause analysis: the calibration of NOx concentration limit is unreasonable and the threshold value is too sensitive. The peak calibration limit shall be changed from 200ppm to 50ppm, and the signal variation range shall be changed from 400ppm to 50ppm. Solution: Brush the latest version of data.
- Permanent fault phenomenon of motor speed deviation of urea supply unit:
① The OBD light is on, no twist limit; ② Fault code: P02AB (permanent fault of motor speed deviation of urea supply unit). Cause analysis: urea pump motor is damaged. Solution: replace BOSCH 2.2 generation urea pump 1161010-51B.
- Crystallization at urea nozzle seat:
The urea nozzle seat is evenly crystallized, and the middle nozzle hole is not blocked, and can be ventilated.
Cause analysis: the urea nozzle seat has local swirl, resulting in a thin layer of urea crystals. Solution: It is a normal phenomenon. If it does not affect the discharge, it does not need to be treated.
- Crystallization at the air inlet of the post-processor:
The air inlet of the post-processor is uniformly crystallized, and there is no large amount of crystalline urea.
Cause analysis: a thin layer of urea crystals will be formed near the interface between the post-processor and the intake pipe during use. Solution: It is a normal phenomenon. If it does not affect the discharge, it does not need to be treated.
- Phenomenon of quality problems of air intake control parts of the rear processor:
① OBD light is on; ② Vehicle torque limit is weak; ③ Urea is not consumed. Cause analysis: when the urea nozzle seat is welded with the exhaust pipe, the "double eyelids" appear, causing urea crystallization, and then blocking the exhaust pipe. Solution: polish the "double eyelid" part.
- Crystallization blockage at the head of urea nozzle:
① After starting, the OBD fault light is always on; ② The engine is limited in torsion and lack of strength; ③ No urea consumption. ④ The urea nozzle head crystallizes and the nozzle hole is blocked.
Cause analysis: the angle between the urea nozzle seat and the exhaust pipe does not meet the BOSCH system engineering design specification.
Solution: replace the exhaust pipe with a new one.
- The camshaft sensor connector is not inserted, resulting in the engine starting difficulty:
① After starting, the OBD fault light is always on; ② The engine is difficult to start; ③ Fault code: P0032 - CAN B passive fault, P00EC - camshaft signal not detected.
Cause analysis: ① CAN B passive fault is a data problem and should be shielded; ② There is no camshaft signal, which makes it difficult to accurately judge the cylinder number when starting.
Solution: ① For P0032 fault, rewrite the latest version of electronic control data released after September 2014 to shield the fault code; ② For P00EC fault, check the camshaft sensor connector.
- Fault performance of automobile oxygen sensor
1)Oxygen sensor poisoning
Oxygen sensor poisoning is a frequent and difficult fault to prevent. Especially for cars that often use leaded gasoline, even new oxygen sensors can only work for thousands of kilometers. If there is only slight lead poisoning, then using a box of unleaded gasoline can eliminate the lead on the surface of the oxygen sensor and make it work normally. However, due to the high exhaust temperature, lead will intrude into the inside of the oxygen sensor, which hinders the diffusion of oxygen ions and makes the oxygen sensor ineffective. At this time, it can only be replaced. In addition, silicon poisoning of oxygen sensors is also common. Generally speaking, the silicon dioxide generated by the combustion of silicon compounds contained in gasoline and lubricating oil, and the silicone gas emitted by the improper use of silicone rubber sealing gasket will cause the oxygen sensor to fail, so it is necessary to use high-quality fuel and lubricating oil. During repair, the rubber gasket shall be properly selected and installed. Do not apply solvent and anti-sticking agent other than those specified by the manufacturer on the sensor.
2) Carbon deposition
Due to the poor combustion of the engine, carbon deposits are formed on the surface of the oxygen sensor, or deposits such as oil or dust are entered into the oxygen sensor, which will hinder or block the external air from entering the oxygen sensor, making the output signal of the oxygen sensor inaccurate, and the ECU cannot correct the air-fuel ratio in time. Carbon deposition is mainly caused by rising fuel consumption and significantly increasing emission concentration. At this time, if the sediment is removed, normal operation will resume.
3)The ceramic of the oxygen sensor is hard and brittle. The ceramic of the oxygen sensor may break and fail if it is knocked by a hard object or blown by a strong airflow. Therefore, special care should be taken when handling, and problems should be replaced in time.
4)Heater resistance wire burnt out
For the heated oxygen sensor, if the heater resistance wire is ablated, it is difficult to make the sensor reach the normal operating temperature and lose its function.