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The camshaft position sensor, also known as a camshaft angle sensor, phase sensor, or cylinder identification sensor, is referred to as the 1st cylinder top dead center sensor in some vehicles. The most common term associated with Hyundai vehicles is camshaft position sensor. The function of the camshaft position sensor is mainly to detect the position and angle of the camshaft, thereby determining the compression top dead center position of the piston in cylinder 1. At startup, the engine ECU uses the signals provided by the camshaft position sensor and the crankshaft position sensor to determine the position and stroke of the pistons in each cylinder, and it controls the sequence of fuel injection and ignition in order to achieve accurate control over fuel injection and ignition. Camshaft position sensors can generally be classified into Hall effect type, inductive type, and AC-excited type. Next, we will use an example of measuring the signal from a Hall-effect camshaft position sensor with an oscilloscope. First, connect a BNC to banana plug cable to channel 1 of the oscilloscope. Then, attach a alligator clip to the black banana plug and connect it to the negative terminal of the battery for grounding, and attach a probe to the red banana plug. A Hall-effect camshaft position sensor typically has three wires: one for the positive power supply, one for grounding, and one for the signal; insert the probe into the signal wire. The oscilloscope channel attenuation should be set to 1X, the time base should be set around 50ms, and the vertical scaling can be set to 1V/div or 2V/div. The waveform of a Hall-effect camshaft position sensor may vary in amplitude; what’s more important is to detect its signal frequency rather than the voltage value. As shown in the waveform below, measured using the oscilloscope cursor, X1 is 1 ms and X2 is -155 ms. By observing the repeating pattern of the waveform, it can be seen that the distance from X1 to X2 constitutes one cycle of this waveform; this distance is 156 ms, so the frequency is the reciprocal of this value, which is 6.41 Hz. Observation shows that the vertical scale of the oscilloscope is set at 2V/div; thus, one grid on the vertical axis represents a voltage value of 2V. The waveform occupies approximately 6 grids in the vertical direction, so the peak voltage of this signal is around 12V. For Hall effect sensors, there are two principles regarding the observed waveforms: first, it is necessary to check whether the signal’s baseline is normal, and second, to verify whether the highest point of the signal falls within the range specified by the manufacturer.