Automotive sensor detection and diagnosis and installation location

Foreword

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With the rapid development of automotive technology and electronic technology, more and more electronic devices are used in automobiles. In automotive electronic control systems, sensors are responsible for the collection and transmission of information. It is only a very important part of the car control system. There are dozens of kinds of automobile sensors. In order to ensure the safe driving of automobiles, the detection and diagnosis of automobile sensors is very important. This paper introduces several methods for detecting and diagnosing automotive sensors, and I hope to help you.

1, car crankshaft position sensor

The automobile crankshaft position sensor is generally mounted on the side of the crankshaft pulley or sprocket, and some are mounted on the front end of the camshaft, in the distributor or on the flywheel.

Automobile crankshaft position sensor detection:

1) Open circuit detection: Turn off the ignition switch, unplug the sensor plug, and measure the resistance value of the induction coil with a multimeter R×10 ohms, generally 300-1500 ohms.

2) Dynamic detection: 1) Measure the output voltage with a multimeter AC voltage file, starting at 0.1V; 0.4-0.8V during operation. Use a frequency meter to measure its operating frequency. Then use a multimeter to measure its voltage signal and use an oscilloscope to detect its signal waveform.

Automobile crankshaft position sensor detection

2, car throttle position sensor

In order to meet the requirements of different working conditions, the sensors of the electronically controlled gasoline injection system mounted on the throttle body are collectively referred to as throttle position sensors.

Throttle position sensor detection:

Linear output throttle position sensor detection

1) Static detection: Use a multimeter to check the resistance value of each terminal compared with the standard. State detection: Turn on the ignition switch and do not start the generator to check whether each terminal is conducting.

2) Dynamic detection: firstly detect the terminal voltage and the continuity of the wire harness, and turn on the voltage signal under the ignition switch measurement and the output of the ECU compared with the standard.

Linear output type throttle position sensor detection waveform

Linear output type throttle position sensor detection waveform

Switch output type throttle position sensor detection

1) Static detection: Turn off the spark plug, remove the sensor harness and use a multimeter to check the resistance value of each end.

2) Dynamic detection: Now detect the continuity of the line and then turn on the ignition switch, and use the multimeter voltage file to detect the supply voltage 12V to start the signal voltage when the engine measures the signal voltage power contact at idle speed.

Switching output type throttle position sensor detection waveform diagram

Switching output type throttle position sensor detection waveform diagram

3, car intake manifold pressure sensor

The vehicle intake manifold pressure sensor is divided into a voltage type automobile intake manifold pressure sensor (semiconductor varistor type, bellows transmission type); a frequency type automobile intake manifold pressure sensor (capacitive type, surface elastic wave type).

The car intake manifold pressure sensor is mounted on the intake manifold, inside the engine compartment, and inside the engine computer.

Automobile intake manifold pressure sensor detection

Automotive intake manifold pressure sensor detection:

1) Open circuit detection: Turn off the ignition switch, unplug the sensor plug, and measure the resistance value of the dynamic resistance of each terminal with the pressure change with the multimeter ohms.

2) When using a multimeter to detect, different gears should be selected due to different signal types. The voltage signal is DC voltage block and the frequency signal is frequency block. Unplug the intake pressure sensor and turn on the ignition switch. Measure the voltage between the VCC and E2 terminals on the harness end plug to 4.5-5.5V. If there is no voltage, check the line and ECU between the ECU and the sensor. Insert the plug back, remove the vacuum hose from the sensor, turn on the ignition switch, and measure the output voltage of the terminal on the ECU connector at atmospheric pressure.

4, car flow sensor

Automotive flow sensors are classified into automotive volumetric flow sensors and automotive mass flow sensors. Installed in air cleaners, throttles, intake manifolds, etc.

1), car volume flow type sensor detection:

Static detection: The multimeter measures the resistance value and the conduction state of each end to dynamically detect the ignition switch, and the air flow rate measures the corresponding resistance value.

Measure the power supply voltage and turn on the ignition switch. Do not start the engine. Use the multimeter to measure the terminal voltage. When the gas flow rate passes, measure its signal voltage. The circuit diagram is as follows:

Vehicle volume flow sensor detection

Measure the power supply voltage and turn on the ignition switch. Do not start the engine. Use the multimeter to measure the terminal voltage. When the gas flow rate passes, measure its signal voltage. The circuit diagram is as follows:

Vehicle volume flow sensor detection

2), automotive mass flow sensor detection

Static detection: Use a multimeter to check the resistance value of each terminal compared to the standard.

Dynamic detection: Turn on the ignition switch and do not start the generator to detect the change of the on-resistance value of each terminal. The circuit diagram is as follows:

Automotive mass flow sensor detection

5, car water temperature sensor

The vehicle water temperature sensor detects the engine cooling water temperature, and inputs a temperature signal to the ECU as a control signal for the fuel injection and ignition timing correction signals of other control systems. It is usually installed on the engine block, on the water jacket of the cylinder head, and at the water pipe joint.

Automotive water temperature sensor

Automotive water temperature sensor detection

1), static measurement multimeter to measure the resistance value of each end of the dynamic detection resistance with temperature changes.

2), unplug the sensor cable and turn on the ignition switch to measure whether the ECU power is 5V and then measure the signal terminal voltage.

6, car camshaft position sensor

The camshaft position sensor is a position signal for collecting the valve camshaft and is input to identify the cylinder compression top dead center, thereby performing sequential injection control, ignition timing control, and knock control. Mounted on the camshaft.

Camshaft position sensor detection

1) Turn off the ignition switch, unplug the wire connector of the cam position sensor, and measure the resistance between the terminals on the cam position sensor with the resistance of the multimeter. If the resistance value is not within the specified range, the crank position sensor must be replaced.

2) Pull out the wire connector of the cam position sensor. When the engine rotates, use the multimeter's voltage file to detect whether there is a pulse voltage signal output between the terminals on the cam position sensor. If there is no pulse voltage signal output, the crank position sensor must be replaced.

Camshaft position sensor detection waveform

Camshaft position sensor detection waveform

7, car speed sensor

The speed sensor includes an engine speed sensor mounted in the transmission; the vehicle speed sensor is mounted on the drive wheel, on the driven wheel, on the rear axle final drive housing, or on the transmission output shaft.

1), automobile engine speed sensor detection

1 Use a multimeter to measure the resistance value of the sensor induction coil. The resistance of the sensor coil is different in different ranges. 2 Use a multimeter to check whether the terminal voltage is a standard value and measure its signal voltage pulse voltage.

2), car speed sensor detection

1 Unplug the vehicle speed sensor connector and measure the resistance at both ends with a multimeter. 2 Different models have different resistances; put the shift lever in the “N” position, turn the wheel by hand, and measure the signal voltage of the ECu end speed sensor with the multimeter voltage block. There should be a voltage indication (pulse voltage). If the display is not normal, the speed sensor line should be checked. If it is normal, the ECU should be checked or replaced. Some models use magnetoelectric speed sensors, and their inspection methods are the same as those of magnetic induction crankshaft position sensors, induction coil resistance and AC voltage signals.

Vehicle speed sensor detection

Conclusion

Automotive sensors (automobile sensor types) are the guarantee for precise control of automobiles. Here we introduce the detection and diagnosis of automotive sensors and their installation positions. Many automotive sensors are tested and diagnosed under specific conditions, and are proficient in the detection of automotive sensors. Diagnostic methods to understand the installation location of the car sensor, many car faults can be solved.

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