8 common sensor faults and solutions

1.Intake pressure sensor

Failure performance:

• ON gear, the engine fault light is always on;

• It emits a small amount of black smoke when stepping on the accelerator slowly, and a lot of black smoke when accelerating rapidly;

• The engine is sluggish;

Reason analysis: The intake pressure signal is abnormal, and the ECU cannot receive the correct intake information, which results in abnormal fuel injection. The combustion is insufficient, the engine is sluggish, and black smoke is emitted during the refueling process. Harness connection problems and sensor failure can cause these phenomena.

Solution: Check the intake pressure and temperature sensor

2. water temperature sensor

Failure performance:

• ON gear, the engine fault light is always on;

• The water temperature in ON mode always displays the maximum value of 120℃;

• The engine has limited torque and insufficient power;

Reason analysis: the water temperature sensor fails, and the ECU uses the substitute value when the output signal of the water temperature sensor is unreliable. The ECU limits the torque of the engine for the purpose of protecting the engine.

Solution: Check the water temperature sensor.

3. oil pressure sensor

• After starting, the oil pressure indicator light is always on;

• The engine fault light is always on;

• Idle speed, the oil pressure value is displayed as 0.99;

Reason analysis: the oil pressure sensor probe is seriously damaged, the ECU detects that the oil pressure sensor is not connected, and the value displayed by the meter is the substitute value inside the ECU.

Solution: Check the oil pressure sensor.

4. OBD socket terminal

Out-of-contact phenomenon：

• ON gear, the power supply of the diagnostic instrument is normal, but it cannot enter the ECU to read the relevant information;

Cause analysis: The OBD socket terminal exits, resulting in poor contact, and the diagnostic instrument cannot be connected to the ECU.

Solution: Check the OBD socket terminal.

5. Nitrogen and oxygen sensor wiring harness

Short circuit phenomenon:

• After starting, the OBD fault light is always on;

• The engine has limited torque and insufficient power

Cause analysis: The nitrogen oxygen sensor wire harness is worn out and cannot work normally, and the system alarms.

Solution: Check the wiring harness of the nitrogen oxygen sensor.

6. Post-processing heating relay box

Failure performance:

• After starting, the OBD fault light is on;

Cause analysis: wire harness open circuit failure.

Solution: Check and repair the wiring harness of the heating relay box.

7. The drive circuit of the urea supply unit is open

Failure performance:

• After starting, the OBD fault light is always on;

• The engine has limited torque and insufficient power;

• Urea is not consumed.

Solution: Check the connector at the end of the urea pump harness.

8. SCR system urea return pipe is blocked

Failure performance:

• After starting, the OBD fault light is always on;

• The engine has limited torque and insufficient power;

• Urea is not consumed.

Reason analysis: the debris in the urea return pipe is blocked, causing the system to fail to spray urea normally, and the system alarms.

Solution: Check the urea return pipe (the urea pipe between the urea pump and the urea tank).