What are the characteristics of sensor failure?
2 Answers
Sensor failure is characterized by unstable idle speed and excessive fuel consumption. Damaged sensors can lead to insufficient engine power, sluggish acceleration, and black smoke from the exhaust. The specific detection methods for sensors are as follows: 1. Check the oxygen sensor heater resistance. Unplug the oxygen sensor connector and use a multimeter's resistance range to measure the resistance between pins 1 and 2 on the sensor side. The specific standard should be checked in the vehicle's repair manual, but generally, it should be between 4 and 40 ohms. If it does not meet the standard value, the oxygen sensor should be replaced. 2. Check the oxygen sensor feedback voltage. Refer to the repair manual of the tested vehicle model to locate the oxygen sensor signal line, and insert a copper wire from the wire into the corresponding pin hole. Then reconnect the connector and use a multimeter's DC voltage range to measure the voltage between the copper wire and the negative terminal. Note that a digital multimeter must be used, and the copper wire must never be grounded, otherwise, the oxygen sensor will be irreversibly damaged. Start the engine and raise the water temperature to at least 80°C. After the engine reaches 2500r/min several times, maintain the engine speed at 2500r/min and observe the voltage displayed on the multimeter. The voltage should rapidly fluctuate between 0.1-1.0V, changing at least 8 times within 10 seconds. If the voltage changes slowly, it does not necessarily mean there is a fault with the oxygen sensor or feedback control system; it may be that the oxygen sensor surface is covered with carbon deposits, reducing sensitivity. In this case, run the engine at high speed for a few minutes to clear the carbon deposits, then observe whether the oxygen sensor signal voltage meets the specifications. If it still does not meet the specifications, conduct a comprehensive characteristic analysis check.
A broken sensor is really annoying. After driving for so many years, I've noticed common symptoms in several aspects. The sudden illumination of the engine warning light is the primary signal, especially for oxygen sensor issues that can cause fuel consumption to skyrocket. For example, highway fuel consumption suddenly increased from 10 liters per 100 km to 15 liters, accompanied by black smoke from the exhaust pipe. There's also a lack of power during acceleration—stepping on the gas pedal only results in sluggish movement, especially noticeable during cold starts, with the engine shaking noticeably as if struggling to breathe. ABS sensor failures are even more dangerous, causing instability in the braking system, with the ABS light flashing on the dashboard. I once experienced wheel lockup during a turn, which nearly caused an accident. Additionally, an inaccurate coolant temperature sensor can lead to engine overheating, where the temperature gauge shows normal readings but the engine is actually boiling over. It's crucial to regularly check for these symptoms—repairs aren't as simple as changing a light bulb. Timely maintenance is essential for safety.
