How to use a multimeter to measure the quality of car sensors
1. To measure the crankshaft position sensor, you need to look at the circuit diagram to determine whether it is active or passive. There are two types of sensors in China, one is a Hall sensor and the other is an electromagnetic sensor. The Hall sensor has three wires, which are 5V power supply, signal, and ground. The measurement method is to use a multimeter to measure the signal with the red probe in the DC voltage range and the black probe directly connected to the negative terminal! Here I want to explain how to measure signals. The sensor is in the car, do not disassemble it, and do not unplug the plug. Use a thin steel wire to measure it by inserting it back into the plug!
After connecting the wires, use a wrench to turn the crankshaft pulley slowly. If the crankshaft position sensor is good, you will find that the multimeter voltage will display 0 degrees and 5 volts at times. Do not turn it too fast yourself. If not, there is a malfunction. The second type is the magneto electric crankshaft position sensor, which has a relatively simple measurement method. Simply unplug the plug and there are two pins inside. Use a multimeter to measure the AC voltage range. Connect the red and black probes to these two pins, and then connect the wires. Start the engine. When the engine crankshaft does not rotate, there is no voltage. Start the engine and you can see a voltage of more than ten volts, which may be higher, indicating good results.
The camshaft position sensor is Hall sensor, and the measurement method is the same as the Hall crankshaft sensor above. It is also connected with a wire. I slowly turn the crankshaft with a wrench to see if there is any voltage change. This requires turning on the ignition switch.
3 intake temperature sensors, intake temperature sensors are now integrated into air flow meters or manifold pressure sensors in vehicle models.
Air flow meter
Its measurement method is also relatively simple. First, look for the circuit diagram and identify the two pins of the intake temperature sensor. The intake temperature sensor is usually a resistor that changes with temperature. Use a multimeter in the resistance range and connect the black and red probes to the two pins found. This sensor needs to be heated with a hair dryer. Check if the resistance changes, if it does not change, it indicates a fault.
The measurement method of the manifold pressure sensor also needs to look for the circuit diagram, see which one is powered by 5 volts, which one is the signal, and which one is the ground. The measurement method is to remove the intake pressure sensor from the intake manifold, do not unplug the plug, use a thin steel wire to plug it back, and lead out the signal. Use a multimeter DC voltage range, connect the red probe to the signal, connect the black probe to the ground, and preferably the negative terminal of the battery! Connect a vacuum cleaner to the interface of the intake pressure sensor and evacuate. It can be seen that the voltage is changing and remains unchanged as a fault
