Where is the engine speed sensor located?
2 Answers
The engine speed sensor is generally installed on the flywheel. The speed sensor on the engine is a Hall sensor, which operates by detecting the signal teeth on the flywheel and converts the magnetic signal into an electrical signal through semiconductor components. This type of sensor can function without direct contact with the measured object. The speed sensor on the transmission can directly convert mechanical signals into electrical signals. The sensor engages with the main reduction gear of the transmission through gears, and the rotation of the main reduction gear drives the sensor gear to rotate, thereby outputting the speed signal. Below are the classifications and functions of sensors on the engine: 1. Crankshaft position sensor. The crankshaft position sensor is used to detect engine speed and provide the crankshaft angle. The ECU uses the crankshaft position signal to determine the fuel injection amount and ignition timing, enabling the car to start normally. The sensor is installed near the flywheel. 2. Coolant temperature sensor. This sensor detects the temperature of the cooling system. When the ECU detects high coolant temperature, it activates the radiator fan to cool the engine, ensuring the engine operates at an appropriate temperature. The sensor is installed on the engine's coolant passage. 3. Intake air temperature sensor. This sensor detects the temperature of the air entering the engine and is primarily used to adjust the fuel injection amount. When the external temperature is too low, it increases the fuel injection, and when it is too high, it reduces the fuel injection. It is installed on the intake air bellows. 4. Intake pressure sensor. To form an appropriate air-fuel mixture, the air drawn into the engine must be precisely calculated. Most vehicles use the pressure value from the intake pressure sensor to determine the intake air volume. The ECU uses this data to determine the fuel injection pulse width and ignition timing. It is generally installed on the intake manifold. 5. Camshaft position sensor. The camshaft position sensor, also known as the phase sensor, is used to detect the top dead center position of cylinders 1 and 4. Combined with the crankshaft position sensor, it starts the engine. It is usually installed near the camshaft. 6. Oxygen sensor. To control vehicle emissions, the ECU monitors the richness or leanness of the exhaust gases to adjust the fuel injection amount, bringing the actual air-fuel ratio closer to the theoretical air-fuel ratio. The oxygen sensor serves this function and is generally installed on the exhaust manifold.
Last time when I helped my neighbor fix his old car, I encountered this exact issue. The engine speed sensor is usually installed near the crankcase, close to the flywheel or crankshaft pulley, as it needs to monitor the rotational speed changes of the crankshaft. Look around the engine area - it's mounted on the lower part of the engine block, a black box smaller than a phone charger with a wire connecting to the ECU. If it gets dirty or fails, the car might not start or experience rough idling. I remember once during replacement, dust had clogged the sensor port - after cleaning it, the RPM returned to normal. Paying attention to this during routine maintenance can prevent lots of trouble.
