How to measure the quality of automotive sensors with a multimeter?
Measurement method of the crankshaft position sensor: First, check the circuit diagram to determine whether the sensor is active or passive. In China, there are two types of sensors, namely the Hall sensor and the electromagnetic sensor. The Hall sensor has three wires, which are the 5-volt power supply wire, the signal wire, and the grounding wire. The measurement method is to use the DC voltage range of the multimeter. Use the red test lead to measure the signal, and the black test lead to directly connect to the negative pole! Here, let me tell you how to measure the signal. When the sensor is installed on the vehicle, do not disassemble it, and do not unplug the plug. Use a thin steel wire to insert and measure from the back of the plug!
After connecting the wires properly, use a wrench to turn the crankshaft pulley slowly. If the crankshaft position sensor is in good condition, you will find that the voltage shown on the multimeter alternates between 0 volts and 5 volts. Don't turn it too fast. If there is no such voltage change, the sensor is faulty. The second type is the magnetoelectric crankshaft position sensor. Its measurement method is relatively simple. Directly unplug the plug. There are two pins inside. Use the AC voltage range of the multimeter. Connect the red and black test leads to these two pins. Then connect the wires properly. Start the engine. When the engine crankshaft is not rotating, there is no voltage. When the engine is started, you can see a voltage of more than ten volts. If there is such a voltage, the sensor is in good condition.
For the camshaft position sensor, if it is a Hall sensor, the measurement method is the same as that of the Hall crankshaft sensor. Connect the wires properly, and use a wrench to turn the crankshaft slowly to check if there is a voltage change. In this case, turn on the ignition switch.
For the intake air temperature sensor, in current vehicle models, it is integrated in the air flow meter or the manifold pressure sensor. Its measurement method is also relatively simple. First, find the circuit diagram to identify which two pins belong to the intake air temperature sensor. Generally, the intake air temperature sensor is a resistor whose resistance value changes with the temperature. Use the resistance range of the multimeter. Connect the black and red test leads to the two identified pins. Heat this sensor with a hair dryer and check if the resistance value changes. If there is no change, the sensor is faulty.
For the measurement method of the manifold pressure sensor, also find the circuit diagram to determine which wire is the 5-volt power supply wire, which is the signal wire, and which is the grounding wire. The measurement method is to remove the intake manifold pressure sensor from the intake manifold without unplugging the plug. Use a thin steel wire to insert from the back to lead out the signal. Use the DC voltage range of the multimeter. Connect the red test lead to the signal wire and the black test lead to the ground, preferably the negative pole of the battery! Connect a vacuum device to the interface of the intake pressure sensor and evacuate. You can observe whether the voltage changes. If there is no voltage change, the sensor is faulty.
