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The intake air pressure sensor is connected to the intake manifold by a vacuum tube. With the different speed loads of the engine, it senses the vacuum change in the intake manifold, and then converts the change of the internal resistance of the sensor is converted into a voltage signal for the ECU to correct the fuel injection amount and ignition timing angle. In the EFI engine, the intake pressure sensor is used to detect the intake air amount, which is called D-type injection system (speed density type). The intake air pressure sensor detects the intake air volume not directly like the intake air flow sensor, but indirectly. At the same time, it is also affected by many factors. Therefore, in the inspection and maintenance, there are many places that are different from the intake air flow of the quantity sensor, and the resulting faults also have its particularity. The intake pressure sensor detects the absolute pressure of the intake manifold behind the throttle valve. It detects the change of the absolute pressure in the manifold according to the engine speed and load, and then converts it into a signal voltage and sends it to the engine control unit. The ECU controls the basic fuel injection amount according to the magnitude of this signal voltage. There are many types of intake pressure sensors, such as varistor type and capacitive type. Because the varistor type has the advantages of fast response time, high detection accuracy, small size and flexible installation, it is widely used in D-type injection systems.

A crank sensor is an electronic device used in an internal combustion engine, both petrol and diesel, to monitor the position or rotational speed of the crankshaft. This information is used by engine management systems to control the fuel injection or the ignition system timing and other engine parameters. Before electronic crank sensors were available, the distributor would have to be manually adjusted to a timing mark on petrol engines. The crank sensor can be used in combination with a similar camshaft position sensor to monitor the relationship between the pistons and valves in the engine, which is particularly important in engines with variable valve timing. This method is also used to "synchronise" a four stroke engine upon starting, allowing the management system to know when to inject the fuel. It is also commonly used as the primary source for the measurement of engine speed in revolutions per minute. Common mounting locations include the main crank pulley, the flywheel, the camshaft or on the crankshaft itself. This sensor is one of the two most important sensors in modern-day engines, together with the camshaft position sensor. As the fuel injection (diesel engines ) or spark ignition (petrol engines) is usually timed from the crank sensor position signal, failing sensor will cause an engine not to start or will cut out while running. Engine speed indicator takes speed indication also from this sensor.

The working principle of the car water pump is that the engine drives the water pump bearing and the impeller to rotate through the pulley, and the coolant in the water pump is driven by the impeller to rotate together, and is thrown to the edge of the water pump shell under the action of centrifugal force.