The G signal and NE signal are generated by the pickup coil, in which the camshaft position sensor or crankshaft position sensor, and the signal plate or the timing rotor. The information from these two signals is combined by the engine ECU to comprehensively detect the crankshaft angle and engine speed. These two signals are not only very important to the EFI systems but to the ESA system as well.
1.Camshaft position sensor (G signal generator)
On the camshaft opposite the camshaft position sensor is a G signal plate with a protrusion(s). The numbers of protrusions are 1, 3, or another number depending on the engine model. (There are 3 protrusions in the illustration.) When the camshaft rotates, the air gap between the protrusions on the camshaft and the sensor changes. This change in gap generates a voltage in the pickup coil built into the sensor, resulting in the G signal. This G signal is sent as the information of the standard crankshaft angle to the engine ECU, which combines it with the NE signal from the crankshaft position sensor to determine the compression TDC (Top Dead Center) of each cylinder for ignition and detect the crankshaft angle. The engine ECU uses this to determine the injection duration and the ignition timing.
When a G signal from the sensor is not received by the engine ECU, there are models where the engine keeps running, and a model where the engine stops.
2.The crankshaft position sensor (NE signal generator)
NE signal is used by the engine ECU to detect the crankshaft angle and engine speed. The engine ECU uses the NE signal and G signal to calculate the basic injection duration and basic ignition advance angle.
As with the G signal, the NE signal is generated by the air gap between the crankshaft position sensor and the protrusions on the NE timing rotor periphery installed on the crankshaft.
The illustration shows a type of signal generator with 34 protrusions on the NE timing rotor periphery and an area with two teeth missing. The area with two teeth missing can be used to detect the crankshaft angle, but it cannot determine whether it is at the TDC of the compression cycle or the TDC of the exhaust cycle. The engine ECU combines the NE signal and G signal to comprehensively and accurately determine the crankshaft angle. In addition to this, some signal generators have 12, 24, or another number of protrusions, but the crankshaft angle detection accuracy varies depending on the number of protrusions. For example, types with 12 protrusions have a crankshaft angle detection accuracy of 30CA.
When the NE signal from the sensor is not received by the engine ECU, the engine ECU determines that the engine has stopped, causing the engine to stop.