Therefore, automobile sensors are very important components for automobiles.
Once a certain sensor fails, the corresponding device will work abnormally or even not work. For example, after the air flow meter fails, the car computer (ECU) cannot detect the true intake of air, resulting in an imbalance of the mixture and an engine Idle speed is unstable, driving is weak and black smoke is emitted, and sometimes the gear shifts and stalls.
The sensor is the input device of the automobile computer system. It converts various operating conditions information during the operation of the automobile, such as vehicle speed, temperature of various media, engine operating conditions, etc., into electrical signals and sends them to the computer so that the engine is in the best working condition. .
Therefore, automobile sensors are very important components for automobiles.
1. Air flow sensor
Air flow sensor is also called air flow meter (AFM), because it measures the amount of air sucked by the engine. Currently, hot wire air flow sensors and hot film air flow sensors are mainly used, which are generally installed between the air filter and the throttle.
Function: Measure the air intake of the engine, and input the signal into the ECU as the main control signal for fuel injection and ignition control.
Failure mode: Generally installed in the air filter and throttle body, once the failure occurs, the engine speed cannot rise. After the air flow meter malfunctions, the car computer (ECU) cannot detect the true intake of air, resulting in an imbalance of the mixture, resulting in unstable engine idling, weak driving and black smoke, and sometimes shifting and stalling.
2. Oxygen sensor
The oxygen sensor can give an alarm when the three-way catalyst is abnormally heated to prevent malfunctions caused by high temperature. The location is on the exhaust pipe, and the oxygen sensor is faulty, so that the ECU cannot know whether the amount of gasoline injected is correct, and the concentration of the mixer is either too rich or too lean, and the combustion is insufficient, reducing engine power and increasing emission pollution.
Function: The fundamental function of the oxygen sensor is to detect the oxygen concentration in the exhaust gas, and then the ECU (engine system control computer) will use the oxygen concentration signal provided by the oxygen sensor to determine the engine's combustion status (pre-oxygen) or the working efficiency of the catalyst (Post oxygen). There are zirconia type and titanium oxide type.
Failure mode: If the oxygen sensor fails, the engine performance is poor, the adjustment is fixed, the idle speed is unstable, the emission value is abnormal, the fuel consumption increases, and the spark plug is deposited. Oxygen sensor poisoning is a fault that often occurs and is difficult to prevent, especially in cars that often use leaded gasoline.
3. Water temperature sensor
is generally installed next to the thermostat. Once it fails, the engine will have difficulty in starting during cold start, unstable idling, and insufficient power during acceleration. The water temperature sensor is actually a semiconductor thermistor. The lower the temperature, the greater the resistance. On the contrary, the smaller the resistance, it is installed on the water jacket of the engine block or cylinder head and is in direct contact with the cooling water.
Function: used to detect the temperature of engine cooling water. The electronic control unit corrects the fuel injection and ignition timing according to the water temperature signal, and installs a water temperature warning light on the instrument panel.
Failure mode: When the water temperature sensor fails (usually poor contact, short circuit, open circuit, but mostly poor contact), the phenomenon is ON, the engine fault light is always on, and the water temperature always displays the maximum value of 120 degrees Celsius, the engine Torque limited and weak, the detected fault code is P003D. If the water temperature sensor fails, the car will experience difficulty in cold start, abnormal fuel supply, weak acceleration, and backfire during rapid acceleration.
4. Throttle position sensor
The throttle position sensor is installed on the throttle to detect the opening of the throttle.
ECU judges the condition of the engine according to the throttle position signal, and controls the fuel injection time according to the demand for the concentration of mixed gas in different conditions of the engine. Throttle position sensor is divided into switch contact type throttle position sensor, linear variable resistance type throttle position sensor, and integrated type throttle position sensor.
Function: The main function of the throttle sensor is to feed back the opening of the throttle to control the amount of fuel injected during acceleration.
Failure mode: abnormal engine idling (such as excessively high or low idling, unstable idling, easy to stall when idling) or abnormal engine acceleration (engine shaking during acceleration, delayed acceleration response, etc.), sometimes causing the engine to run Phenomenon such as intermittent jitter occurs.
5. Crankshaft position sensor
The crankshaft position sensor and the engine speed sensor are integrated, used to determine the position of the engine crankshaft, the position of the top dead center and the engine speed. The crankshaft position sensor (CKP) is one of the most important sensors in the engine centralized control system, and it is an indispensable signal source for confirming the crankshaft angle position and engine speed.
Function: The engine control module (ECU) uses this signal to control the fuel injection volume, fuel injection timing, ignition timing (ignition advance angle), ignition coil charging closing angle, idling speed and the operation of the electric gasoline pump.
Failure mode: The crankshaft position sensor is broken, and the crankshaft rotation angle cannot be confirmed. The engine computer cannot receive the signal from the crankshaft position sensor. In order to protect the engine from ignition or fuel injection, the sign of the car is that there is no high voltage electricity. , No fuel injection, no driving.
6. Knock sensor
is generally installed on the cylinder wall of the engine. Once it fails, the engine fault light will be on and the engine will appear "self-protection", which will affect normal driving.
Function: The knock sensor is used to detect whether knock occurs during the combustion process of the engine, and send the knock signal to the engine control computer as an important reference signal for correcting the ignition advance angle.
Failure mode: When the knock sensor fails, the engine will deflagrate, the ignition timing will be inaccurate, high fuel consumption, low power, difficult to start, and rough engine operation.
7. Intake air pressure sensor
Intake air pressure sensor is referred to as MAP sub-resistive intake air pressure sensor and capacitive intake air pressure sensor. It is generally installed next to the throttle valve. If it fails, it will cause a series of problems such as difficulty in ignition, unstable idling, and weak acceleration.
Function: Detect the absolute pressure of the intake manifold, then convert it into a voltage signal and send it to the ECU. The ECU controls the basic fuel injection volume according to the signal voltage.
Failure mode: The fuel injection quantity can not be controlled normally, causing the mixture to be too thick or too lean, causing the engine to run abnormally, and the idling will also be unstable, often stalled, fuel consumption soaring, or even unable to start when it is severe.
8. Intake air temperature sensor
detects the intake air temperature and inputs the intake air temperature signal to the ECU as a correction signal for fuel injection and ignition timing.
is generally installed behind the throttle, once the faulty engine is too rich or too lean, it will directly lead to difficulty in cold start and unstable idling after starting
A car is a "complex body" composed of thousands of parts. Various sensors make people look dizzy. If each sensor fails, the normal operation of the car will be greatly reduced!
