Analysis of 11 classic failure cases of ultrasonic transducer sensors

After testing, the gasoline pressure at idling speed is 260Kpa, and it can reach 310Kpa when ultrasonic wind speed measurement is accelerating, indicating that the oil pressure is normal. Read the data stream, the air mass flow rate at idling speed is 2.2g/s, which is lower than the normal value (2~4g/s). It is suspected that the air flow meter is faulty, and the fault remains after replacement. Then check the vacuum degree with a vacuum gauge, and the vacuum value is 16 (normally 60~70Kpa), which proves that the intake system is leaking. After checking the outside of the intake pipeline with soapy water, no leaks are found. After thinking about it, I unplugged the vacuum line connected with the activated carbon tank solenoid valve and blocked it with my fingers. It was found that the vacuum value suddenly rose to 65Kpa. After careful inspection, it was found that the activated carbon tank solenoid valve was stuck in the high position, and the fault disappeared after replacement.

[Case 2]  Engine stall failure occurs when it is stepping on the brake pedal.

Trouble phenomenon: When the brake pedal is depressed, the deceleration effect is not very good. At the same time, the engine violently shakes for a few times and then stalls, and the vehicle loses control and continues to slide forward.

Failure analysis:

1. If the brake is stalled for the manual transmission model, 200Khz ultrasonic transducer

Is consider whether it is a normal phenomenon of the stalled brake.

2. Braking is equivalent to releasing the accelerator pedal in a sense, considering the idling motor is stuck in the low position.

3. Vacuum leakage occurs when the vacuum booster is braking

Troubleshooting:

1. Because the car is automatic transmission, the stalled brake is not considered

2. Detect no fault code

3. After investigation, the engine idling speed is stable and stable at about 850 rpm, which meets the normal requirements. It shows that the non-idling motor is stuck in the low position.

4. Step on the brake pedal in the idling state, the engine will tremble violently for a few times and then it will turn off, and the pedal will feel hard. This can only be caused by vacuum leakage. However, due to idling speed and normal driving, the engine is running normally, so the vacuum line connecting the vacuum booster and the intake manifold is not considered, so the master locks the fault on the vacuum booster.

5. Connect the vacuum gauge to the intake manifold to detect. The vacuum degree is 64Kpa at idling speed. When the brake pedal is stepped on (the engine starts to shake but does not turn off), the vacuum degree drops to 15Kpa. There is only a booster (the vacuum tube is very thick) that can have such a large amount of air leakage in the intake system. After replacement, the fault is eliminated.

Troubleshooting:

The left and right air chambers inside the vacuum booster cannot be properly sealed during braking. As a result, a large amount of air enters the left air chamber during braking, and then enters the combustion chamber through the one-way valve and vacuum pipeline. Because the car uses an air cylindrical ultrasonic transducer, it cannot sense the amount of intake air behind the throttle, causing the mixture to become too lean and stall.